VIEWS: 209 PAGES: 86



                      TECHNOLOGY ROADMAP FOR
                      ORTHOTICS & PROSTHETICS

                                  VERSION 1.0
                               SEPTEMBER 24, 2007

                                 SUBMITTED BY:


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This draft report was produced by the Integrated Manufacturing Technology Initiative (IMTI,
Inc.) under prime contract No. GS-1OF-O21OL for the Next Generation Manufacturing Tech-
nology Initiative (NGMTI) Program. This report provides recommendations to guide research
and development and program planning by U.S. federal agencies and industry to advance the
readiness of orthotics and prosthetics technologies for manufacturing and deployment to the na-
tion’s warfighters and civilian sector.
Funding for this effort is provided through the Defense Logistics Agency. Primary input for this
report was gathered at a government/industry workshop conducted in June 2007 in Silver Spring,
Maryland. The workshop was conducted by the Composites Manufacturing Technology Center
(CMTC) with the support of the Next-Generation Manufacturing Technology Initiative
(NGMTI) program and facilitated by the Integrated Manufacturing Technology Initiative (IMTI).

This draft document is a work in progress. All reviewers are invited to provide feedback and
recommendations. Please direct your comments to Dr. Rob Steele, IMTI project coordinator, at
The authors of this document have no connection with any organization involved in orthotics or
prosthetics, and the information presented here is not intended to promote any particular technol-
ogy, product, or process. It is the intent of the project team to provide equal and fair assessment
and recording of all input provided.

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1.0 INTRODUCTION ........................................................................................................................ 4
   1.1   Background........................................................................................................................................ 4
   1.2   The Need: Acceleration of Orthotics and Prosthetics Advances ....................................................... 4
   1.3   Orthotics & Prosthetics Overview ..................................................................................................... 6
   1.4   Roadmapping Methodology .............................................................................................................. 7
   1.5   The Vision ......................................................................................................................................... 9
   1.6   The “Nuggets” ................................................................................................................................... 9
2.0 PRODUCT LIFE-CYCLE MANAGEMENT................................................................................. 15
   2.1   Current State Assessment for Product Life-Cycle Management ..................................................... 16
   2.2   Vision for Product Life-Cycle Management ................................................................................... 24
   2.3   Issues and Solutions for Product Life-Cycle Management ............................................................. 26
   2.4   Roadmap for Product Life-Cycle Management ............................................................................... 32
3.0 ADVANCED MATERIALS APPLICATIONS ............................................................................... 34
   3.1   Current State Assessment for Advanced Materials Applications .................................................... 34
   3.2   Vision for Advanced Materials Applications .................................................................................. 46
   3.3   Issues and Solutions for Advanced Materials Applications ............................................................ 48
   3.4   Roadmap for Advanced Materials Applications.............................................................................. 55
4.0 ELECTRONICS & PROCESSING .............................................................................................. 58
   4.1   Current State Assessment for Electronics & Processing ................................................................. 58
   4.2   Vision for Electronics & Processing ............................................................................................... 66
   4.3   Issues and Solutions for Electronics &Processing........................................................................... 67
   4.4   Roadmap for Electronics & Processing ........................................................................................... 72
APPENDIX A WORKSHOP PARTICIPANTS .................................................................................... 73
APPENDIX B GLOSSARY OF ORTHOTICS AND PROSTHETICS TERMS ......................................... 75
APPENDIX C ACRONYMS AND ABBREVIATIONS .......................................................................... 85

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                                  1.0 INTRODUCTION

In June 2007, representatives of more than two dozen companies, government agencies, and aca-
demic organizations met in Silver Spring, Maryland to begin the process of developing a tech-
nology roadmap for orthotics and prosthetics. The project is sponsored by the Department of
Defense (DoD) Office of the Secretary of Defense (OSD) Manufacturing Technology Program
through the Defense Logistics Agency (DLA) and the Navy Manufacturing Technology Program.
The workshop attendees participated in a combination of plenary and small-group sessions. This
“technology summit” of experts, practitioners, users, and visionaries from the orthotics and pros-
thetics development and manufacturing community took advantage of this unique opportunity to
help chart a future that will exploit the potential technological direction and deliver breakthrough
advances for this critical area.
This draft roadmap accomplishes a significant mid-step in the process of developing a strategic
investment plan (SIP) for the orthotics and prosthetics area. A Red Team review of this docu-
ment by subject matter experts from all stakeholder groups will validate the document and pro-
duce a list of project areas with supporting white papers. These white papers will include a busi-
ness case indicating how investment in those technologies should proceed and a technology
management plan for continuing the effort until the vision is achieved.
Several factors have increased the importance and visi-
bility of orthotic and prosthetic devices over the past           A Technology Focus
several years. Improvised explosive devices (IEDs)                 – Without Blinders
used by insurgents in the ongoing Middle East conflicts      The intent of this project, from the
are inflicting an inordinately high number of injuries to    workshop to the delivered documents
limbs and extremities. At the same time, advances in         and including the projects that could
forward surgical and medical care, coupled with im-          result, is to provide a technology
                                                             roadmap to lead the Government’s
proved body armor and evacuation techniques, have            investments in addressing technical
helped soldiers survive wounds they likely would not         barriers to improved orthotics and
have survived in earlier military conflicts. A growing       prosthetics. However, cultural and
number of military personnel need assistive devices,         business issues abound in every area
and they deserve the best that technology can provide.       addressed.      Recognizing that the
                                                             non-technical issues must be ad-
Many wish to return to duty, and need the tools and de-      dressed to achieve the vision, this
vices to help them achieve that goal.                        document attempts to light a pathway
                                                             to technological excellence while
The DoD has a clear mission to provide the best possi-       highlighting those business and cul-
ble care for the wounded warrior with an ultimate goal       tural issues that can not be ignored.
of enabling servicemen and servicewomen to return to
their highest level of activity, whether they return to active duty or transition into Veterans
Health Administration programs and the civilian community. These factors drive the need not
only for improved functionality and performance of orthotic and prosthetic devices, but for im-
proved manufacturability and reduced cost.

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The civilian population can expect significant spin-off benefits in this area since changes in the
civilian sector have also driven the need for advances in orthotics and prosthetics. As the Baby
Boom sector of the population ages, the next two decades will see a sharp increase in the need
for rehabilitation and disability technology and services to deal with stroke, trauma, developmen-
tal disabilities, osteoarthritis, and other age-related conditions. It is conservatively estimated that
there are approximately 2 million Americans living with limb loss today, which equates to about
one of every 200 people in the United States.
The need for prosthetic care in the civilian sector, including former warriors, is also driven by
vascular disease caused largely by complications from diabetes, to which obesity is a major con-
tributing factor. Twenty million Americans have diabetes and another 41 million are considered
pre-diabetic. An estimated 60 million Americans are defined as obese, equating to nearly 30%
of the U.S. population.
Medicare data also demonstrate that the need for orthotic and prosthetic care will continue to in-
crease. In 2002, 1.9 million Medicare beneficiaries (5.8% of all Medicare patients) made a claim
for orthotic or prosthetic care. This was up from 1.4 million beneficiaries (4.4%) in 1999. This
contrasts with just a 7.1% increase in the number of Medicare beneficiaries over this same period.
Medicare data also suggest greater demand for orthotic and prosthetic care in younger age groups,
suggesting that quality care will be pivotal in enabling people with disabilities to return to work,
live independently, and improve the quality of their lives.1
DoD Needs: A Closer Look
Individuals who enter military service are typically young and in excellent health. Their expec-
tations to return to high activity levels after injury continue to challenge healthcare providers and
health technology engineers to improve prosthetic designs, therapeutic intervention, and training.
A recent cultural shift in the military has helped to retain soldiers with amputations who desire to
remain on active duty. It is important to track these statistics and make comparisons to figures
from previous military conflicts. Kishbaugh et al. reported a return-to-duty rate of 2.3% among
amputees after the first Gulf War. Statistics for the current conflict are not yet available, but sig-
nificantly higher rates are expected. Those most likely to continue to serve have below-the-knee
U.S. troops injured in Iraq have incurred limb amputations at twice the rate of past conflicts. On-
ly one in 10 troops injured in Iraq or Afghanistan has died, which is the lowest rate of any war in
U.S. history. Data compiled by the U.S. Senate and included in the 2005 defense appropriations
bill to increase funding for the care of amputees at Walter Reed, reveals that 6% of those wound-
ed in Iraq have required amputations, compared with 3% for past wars. In World War II, about
30% of those wounded died; in Vietnam the figure was 24%3.

  Peter Thomas, “Testimony of the Orthotics and Prosthetics Alliance before the Interagency Committee on Disability Research (ICDR),
   May 23, 2006.
  Sig Christenson, “Amputee still fighting” http://iamputees.blogspot.com/2005/04/amputee-still-fighting.html

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These factors emphasize the imperative for achieving significant advances in orthotics and pros-
thetics technology. The solutions lie in the domains of lightweight, affordable, fit/function cus-
tomizable, and highly functional devices. Rapid improvements in materials, manufacturing pro-
cesses, and electronics technology point toward realization of the vision. However, the limita-
tions of available resources require stronger focus and greater return on technology investments
to achieve the needed advances in the design and production of orthotic and prosthetic devices.
This section provides a general orientation summary of past, present and future orthotics and
prosthetics development and direction. The intent is to highlight and reinforce the inherently
creative, innovative, and evolutionary orthotics and prosthetics environment – grounded in ne-
cessity and pragmatism, but consistently looking for improvements.
Historical Perspective
Assistive and replacement limb devices have been part of the human condition for thousands of
years. Orthotics began with the ancient art of splint and brace making. Prosthetics has been
closely associated with amputation performed as a lifesaving measure from an accident or the
aftermath of battle. Historically, each major battle has been the stimulus for improvement of
medical care, amputation techniques, and development of improved ortheses/prostheses.
Ancient cultures used available materials and skills to fashion simple crutches or wooden and
leather cups. This evolved into a type of modified crutch or peg to free the hands for everyday
The Egyptian, Greek, and Roman civilizations developed the scientific approach toward medi-
cine and subsequently prosthetic science. Pliny the Elder wrote of Marcus Sergius, a Roman
general who sustained injuries and a right arm amputation during the second Punic War (210
BC). An iron hand was fashioned to hold his shield, and he returned to battle.
However, it was not until the 20th century that WWI and WWII and the polio epidemics of the
late 1940s and early 1950s stimulated the most significant contributions to orthotic and prosthet-
ic sciences. Injured veterans who acquired musculoskeletal and neuromuscular impairments or
traumatic amputation returning from combat in Europe ushered in an era of change4.
In late 1945, the Veterans Administration (VA) centralized its prosthetics operations under a new
Prosthetic Appliance Service. By December 1945, Congress gave the VA broad authority to
provide prosthetic appliances. Surgeon General of the Army Norman T. Kirk started this process
with a meeting of prosthetics experts in January 1945 at Northwestern University. The meeting
was pivotal for two reasons: it marked the birth of federal funding for rehabilitation research, and
it established the fields of science, medicine, and engineering as integral to prosthesis develop-
ment. The meeting pushed prosthetics beyond craft and into the realm of science.5
Present Perspective
Since then, the science and business of orthotics and prosthetics has expanded rapidly, fueled by
government, industrial, and medical response plus increasing user activism after WWII and sub-
sequent conflicts. Advances in areas such as manufacturing, materials science, electronics, com-

    “History of Prosthetics and Orthotics”; http://www.ap.gatech.edu/mspo/history.htm
    “The Evolution of Prosthetics”, VAngard; http://www.va.gov/opa/feature/vanguard/index.htm; May/June 2005

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puting, biology, bio-mechanics, neuroscience, robotics, and sensors have produced a wide varie-
ty of readily available orthotic and prosthetic solutions.
The methodology to develop the Orthotics and Prosthetics roadmap began with subject matter
experts adopting a functional taxonomy which segregates the topic into logical areas to focus
discussions and planning. This taxonomy subdivided orthotics and prosthetics into three areas of
particular interest to the manufacturing community: Product Life-Cycle Management, Advanced
Materials Applications, and Electronics and Processing, with further subdivision below each.

        Figure 1-1. The roadmapping methodology uses a functional model of the topic area
                    to guide exploration of issues and development of solutions.

On June 26 and 27 NGMTI hosted a workshop for 44 subject matter experts in Silver Spring,
MD near the Walter Reed Army Medical Center. A list of participants is provided in Appendix
In her welcoming remarks, Adele Ratcliff of the Office of the Deputy Under Secretary of De-
fense (Advanced Systems and Concepts) Technology Transition reviewed the scope of the
content typically covered at the annual Defense Manufacturing Conference (DMC). She report-
ed that OSD determined that there needed to be a joint industry/government forum to grow fur-
ther from the topics discussed at DMC. Dr. Brandon Goff, from Walter Reed, spoke at the last
DMC. His presentation was eye-opening to OSD. Ms. Ratcliff said, “This workshop provides
an opportunity to further identify a landscape where we can remove the technical barriers for the
wounded warfighters that restrict the current products. It should be our goal to give these warf-
ighters what they need, not just to survive, but to prosper in military and civilian environments.”
Joe Miller, Chief Prosthetic and Orthotic Service, Integrated Department of Orthopedics
and Rehabilitation, National Naval Medical Center/Walter Reed Army Medical Center,
cited many statistics supporting the theme that advances in the design and production of orthotic
and prosthetic devices will have a significant impact not only on the lives of the recipients, but in
the cost of their supply and maintenance. The challenge he offered the group included reducing
the manpower required to produce a device, increasing the accuracy and ease of moving data

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from one manufacturing software package to another, reducing material waste in fabrication, de-
veloping an economic model that encourages reimbursements for the use of new technologies,
and increasing users’ access to new technology.
Lieutenant Colonel John Alvarez (DoD’s first helicopter pilot to return to flight status and
combat as an amputee) offered his view on what the group should do from a user’s perspective.
“First, we need to realize that the warfighter views his prosthetic as an ‘operational’ rather than a
‘medical’ device,” he said. He credited the expeditionary medical evacuation team concept with
revolutionizing the process for getting soldiers back quickly to capabilities and also in combating
high levels of infection that were typical in past processes.
Col. Alvarez pointed out that the user’s priorities include comfort – without it, they will not use
the prosthetic. This goes for all of the constructs, including the joints. The prosthetist also must
       Stability/fit – based on what type of activity is important
       Will it help the user get the job done? Beyond the high technology that is used, the main
        issue is, “does it work for me?”
            o Performance – running/physical training
            o Reliability and ruggedness
            o Simplicity and ease of use
       Aesthetics (low on the priority list for military users).
       And again, Comfort
John Register, Associate Director of Outreach for the U.S. Olympic Committee (USOC),
reminded the participants that it is not only the military that desire to return to a very active life-
style but that many civilians must also overcome an amputation or limb weakness to fully engage
in life. “The USOC focuses on removing boundaries, because boundaries often draw us into
thinking that we can’t achieve the goals and objectives that we had in the past,” he said. “The
Paralympics shows the phenomenal capability of the individual spirit and the ability to move past
those boundaries. Civilians will also benefit from anything the military can do to improve the
form, fit, and function of orthotic and prosthetic devices.”
The workshop accomplished its primary goal of providing input to this roadmap in three small
groups focused on Product Life-Cycle Management, Advanced Materials Applications, and
Electronicsand Processing. In these groups the subject matter experts developed an assessment
of the current state of their areas as related to orthotics and prosthetics, identified current barriers
that constrain progress, and articulated visions of how technologies in these areas should be in
the future, approximately 10-15 years out. On the second day the groups defined the issues that
must be addressed in order to achieve the vision, and then identified recommended solutions (ac-
tions) to address the issues.
Because, the two-day workshop provided insufficient time to delve deeply into any one topic,
this document incorporates additional research by the project team, and reference material pro-
vided by the workshop participants, to more fully articulate the issues and the solutions.

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In reviewing the document as it developed, several solutions stand out as priority actions that of-
fer high potential for near-term impact, or which are precursors to enable other, downstream so-
lutions. These “nuggets” are discussed in the following sections.
The overall vision derived at the workshop is:
            Future orthotic and prosthetic devices will not limit the lifestyle of the user.
While each of the three main sections in this document articulates a 10- to 15-year vision for
their area, they all align to envision the following:
      Every recipient of an orthotic or prosthetic device will receive a best total solution that re-
       stores their full quality of life.
      A full knowledge of materials properties, design possibilities, and manufacturing processes
       coupled with advanced models of human anatomy and prosthetic systems will enable pros-
       thetics that act, feel, and look at least as good as the original natural limb while enabling
       full return to natural functionality.
      The technologies, the business systems, and the cultural issues will all mold together to de-
       liver the best total value for the person most affected: the user.
      “Smart prosthetics” will adapt in real time to the user’s needs and assume an increasing
       level of motor control in concert with evolving user experience and capability.
A number of solutions stand out as actions to pursue first because they provide near-term impact
or support downstream solutions to accomplish the vision. These critical solutions fall into three
categories: Technology, User and Practitioner, and Business as described below.
The six technology nuggets form three groups as shown in Figure 1-2; two deal with advancing
basic knowledge and developing some fundamental tools; three deal with advancing device func-
tionality; the third area deals with moving the manufacturing process from artisan-based, hand-
customized structures to manufacturing them right the first time, automatically. These are drawn
from the collection of issues and solutions discussed in more detail in the body of this document.
In the opinion of this document’s authors and the participating subject matter experts, DoD
should immediately request the funding to pursue projects in the six technical areas and find
ways to encourage societies, businesses, and other groups to work toward resolutions of the non-
technical issues.
      1. Systems of Models: Computer models must be developed for mechanics, materials, dy-
         namic physics and the integrated, customized control and operation of the devices. Also
         included are models of the geometrically and anatomically correct human body to which
         the devices must interface, to drive the design, manufacturing, and use of these devices.
         To provide prosthetic devices with highly natural functionality and the ability to adapt
         and lead the user into increasing capability, there must be improved understanding and

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        ability to model human motion and motor control (including the neural system, muscles,
        and joints). “Composable” models of prosthetic devices must be able to be assembled us-

Figure 1-2. The six Technology Nuggets are interrelated elements of the larger solution space.

        ing models of their components, materials, and functional capabilities. These models can
        then be integrated and customized for any user, and optimal control and adaptation strat-
        egies devised to suit capabilities and functional needs. Only with this level of under-
        standing and detailed modeling capability can the user be led from initial first steps to
        restoration of full, natural function and ability to take on new physical challenges.
    2. Enhanced Manufacturing: Model-based design must be accompanied by capabilities
       for model-based product realization including conceptualization, detailed design, produc-
       tion, and life-cycle support.
        Present orthotics and prosthetics design and manufacturing processes lack the integration
        needed to deliver cost-effective solutions and optimized life-cycle service and satisfaction.
        The product life-cycle should be an integrated process that starts with the definition of
        user’s needs. From this definition and resulting requirements tied directly to the diagno-
        sis, alternatives can be evaluated leading to the definition of the product (and the process-
        es used to create it) that obtain the best possible balance in addressing manufacturing and
        long-term patient concerns. The concepts chosen through the evaluation process drive
        the detailed design, which in turn captures the full product intent and is complete enough
        to drive all downstream applications, not only for device manufacture and user delivery

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        and training but also through ongoing support adjustments for changing user needs
        through the years. This will reduce costs for all invested parties and provide the best ful-
        fillment of the user’s needs.
    3. Mechanical/Neural Information Exchange: Biomechanical and neural information ex-
       change technologies and human deployment must be improved.
        A key problem arising in any discussion with prosthetics practitioners is the indirect and
        indistinct communication between the human brain and body and the engineered device
        for purposes of functional control and sensory feedback. The user needs a natural mech-
        anism to send control signals to the prosthetic, and the traditional, typically muscular sig-
        nals must give way to more direct and detailed neural communication. As neural com-
        munication develops, users will be able to receive sensory feedback from the environ-
        ment, the results of ongoing actions, and closed-loop response and control becomes pos-
        sible. Until the gap between the user’s neural system and the device is closed, the truly
        “natural” prosthesis will remain elusive.
    4. Materials Capabilities: Biocompatible and other high-performance materials for stable
       and long-term durability must be developed.
        Biocompatible materials are needed to support increasingly invasive medical procedures
        involving neural implants, implantable myoelectric sensors, and osseointegration. Lack
        of adequate materials for such devices and lack of knowledge regarding the body’s long-
        term exposure in hyper-sensitive nerve areas make small size and biocompatibility key
        features of new materials development. The body environment is demanding and a lack
        of appropriate materials may jeopardize not only the efficacy of new procedures, but
        could prevent promising medical solutions from being viable. Similarly, as expectations
        for orthotic and prosthetic performance and natural functionality increase, so do the ex-
        pectations for materials. Central to this issue is the need for durable long-life materials
        able to operate in an increasingly intense usage environment. The requirements of the
        environment should dictate the functionality of the materials used rather than materials
        shortfalls constraining performance limits as is currently the case.
    5. Intelligent and Adaptable Devices: Device systems must be developed that can ac-
       commodate physical changes over time and use, including hardware and software that al-
       low interaction and adaptation to the user’s activity level.
        “Return to full natural functionality” is a recurring theme for the orthotics and prosthetics
        environment. This is a serious challenge for artificial/non-living systems and materials.
        Real-time integration and interaction with the users’ bodies and adaptation to their chang-
        ing activities and environments are essential. Advances in biomimetic engineering, mi-
        cro/nano technologies, and materials science are needed to enable new materials coupled
        with designs and sense-and-control technologies that can adapt like living systems. Con-
        trol systems must provide progressive amounts of challenge to the user as recovery and
        capability increase, and as the user learns to operate the device’s functionality, without
        limiting the user at any point. This requires analysis of feedback and adaptation from the
        prosthesis/orthosis to support and “lead” the user to more natural function.
    6. Device Function and Responsiveness: Sensing, actuation, energy, and power technolo-
       gy must be improved.

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        Advances in sensor technology and the need for better control mechanisms increase the
        need to sense and process huge amounts of various types of data, and to pack sensors and
        processors into ever-smaller components. These developments are accompanied by ur-
        gent needs for increased power delivery; powerful, instant-response actuators; and light-
        weight, long-term energy storage within the prosthetic devices. Because the durable
        medical equipment industry may not provide the main impetus for some of these core
        technologies, developments across all industries must be monitored to harness and adapt
        the most promising technologies for use in prosthetics.
User and Practitioner
    7. Users: Enhanced training and support must be provided for users to assure maximum
       synergy and neural adaptation between prosthesis and user.
        A customized high-fidelity model of the user and his/her prosthetic devices will enable
        better understanding of the physical limits and current capabilities of the user and how to
        exploit the neural plasticity of the user (both mentally and with muscle/tendon changes).
        With this specific knowledge and a training paradigm supporting continual growth as the
        user and prosthesis adapt to each other, the prosthetist can tune the parameters of the de-
        vice to support the user in regaining lost functions and the ability to generalize to new
        functional situations.
    8. Practitioners: Continuing education and aligned certification programs must be provided
       to support current and emerging technologies and applications.
        Dedication to orthotics and prosthetics service is a life-long commitment that should be
        coupled with lifelong learning. The field moves quickly, and emergence of new technol-
        ogies dictates a strong need for updated training and education. The education systems
        are tied to the certification process in that they must prepare their students for success as
        Certified Prosthetists-Orthotists (CPOs). The certification process often does not keep
        track with the pace of technological advance. Harmonization of certification with educa-
        tion and lifelong learning is an industry imperative.
    9. Information Exchange: Mechanisms must be provided for access, exchange, and unifi-
       cation of information resources to ensure readily available knowledge of orthotics and
       prosthetics technologies and directions across the industry including standardized no-
       menclature and procedures. .
        A wealth of information already exists in the orthotics and prosthetics environment and
        related areas. Straightforward, rapid, and timely access to this existing knowledge and
        the rapidly growing base of new developments is critical to raising the standard of care
        provided by the orthotics and prosthetics profession. New developments in other indus-
        tries must be identified, data sifted for orthotics and prosthetics use, and made available
        promptly across the community. Information sharing may come in many forms, such as
        online newsletters, shared data sources, or professional workshops or meetings. Leverag-
        ing information technology at all levels of practice is needed to ensure consistently high-
        quality, cost-effective, and technologically beneficial solutions are shared and imple-

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        10. Cost Coverage Issues: User support and reimbursement practices must be developed
            based on diagnosis and desired results rather than focusing on devices purchased.
             Present reimbursement and business practices are inconsistent across states and insurance
             companies. Parity laws in several states mandate that insurance companies cover pros-
             thetics. However, reimbursement practices are typically counterproductive, supporting
             payment for devices or products instead of payment based on diagnosis and services for
             the specific needs of that person. Users generally need multiple, sometimes many, sup-
             port visits for their training or to adjust the devices to their needs, often without requiring
             purchase of additional (reimbursable) products. A number of changes are needed, start-
             ing with consistent, nation-wide coverage of orthotic/prosthetic practice by insurance
             companies. Clear and uniform definition of prosthetic rehabilitation, standards for evalu-
             ating users’ needs and tying those needs to a plan for care, clear linkage between emerg-
             ing concepts and the deployment/insurance community, and other coordinated actions
             will result in a system that potentially reduces costs across the board while assuring the
             best result for the user.6
        11. Medical-Prosthetics Interface: Prosthetics considerations must be integrated with am-
            putation surgery planning and execution.
             Prosthetic devices have advanced enough in sophistication and functionality that much
             finer controls are needed, much more closely connected to the user’s neural system.
             There are also developments toward osseointegration for limb replacement, instead of the
             traditional socket-and-liner interface. Thus the field of prosthetics treatment is inexora-
             bly overlapping with medical concerns where surgical amputations are involved. To help
             deliver the best result for the user, a prosthetist must be involved in the surgical planning
             to ensure an optimal solution and fit for high-function prosthetic devices. Such multi-
             disciplinary treatment must be standardized and codified for appropriate reimbursement,
             as required for hospital treatment. These revised standard procedures must be published
             in widely used information sources and included in all medical education.

    Deanna Fish, http://www.oandp.org/jpo/library/printArticle.asp?printArticleId=2006_01S_125

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The following table provides a cross reference relating these 11 nuggets to the numerous indi-
vidual solutions supporting them developed at the workshop and found later in this document.

                                    CROSS REFERENCE NUGGET TABLE

 1. Systems of Models
    2.1.1, 2.1.2, 2.1.3, 2.1.4, 2.2.1, 2.2.3, 2.5.3, 3.1.3, 3.1.4, 3.1.5, 3.4.3, 3.4.4, 3.4.5, 3.4.6, 3.8.4,
 2. Enhanced Manufacturing
    2.1.1, 2.2.2, 2.4.1, 2.4.2, 2.6.1, 2.6.2, 2.9.1, 2.10.1, 3.2.3, 3.7.1, 3.7.3
 3. Mechanical/Neural Information Exchange
    2.3.1, 3.5.1, 4.2.1, 4.2.2, 4.3.1, 4.3.2, 4.4.1
 4. Materials Capabilities
    2.4.1, 3.1.2, 3.2.2, 3.2.5, 3.4.1, 3.5.1, 3.5.2, 3.5.3, 3.5.4, 3.5.5, 3.7.2, 3.7.3, 3.8.1, 3.9.1, 3.9.2,
    3.9.3, 3.9.4, 4.4.3
 5. Intelligent Adaptable O&P
     2.3.1, 3.1.1, 3.2.1, 3.3.3,
 6. Device Function and Responsiveness
    2.1.1, 2.3.2, 2.9.3, 3.3.1, 3.3.2, 3.8.2, 3.8.3, 3.10.1, 3.10.2, 4.4.1,
                                         Users and Practitioners
 7. Users:
    2.9.3, 4.2.1, 4.2.2, 4.5.1,
 8. Practitioners
    2.9.1, 2.9.2, 2.9.4, 4.1.2, 4.1.3, 4.5.2
 9. Information Exchange
     2.6.1, 2.6.2, 2.10.2, 4.1.1,
10. Cost Coverage Issues
    2.5.4, 2.7.1, 2.7.3, 2.7.4, 2.8.1,
11. Medical-Prosthetics Interface
    2.9.4, 3.6.1, 3.6.2, 3.63, 3.6.4

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Product life-cycle management embraces all the activities involved in designing, developing,
producing, and supporting orthotic and prosthetic devices. The functional model for the topic
area (Figure 2-1) addresses all elements of the product life-cycle, from innovation and conceptu-
alization of product concepts, through detailed design, through the manufacture of products, and
including the life-cycle support of the products.

                       Figure 2-1. Orthotics and Prosthetics Functional Model
The sub-elements of product life-cycle management are defined as follows:
     Innovation and Conceptualization – Innovation and conceptualization start with identify-
      ing end-user wants and needs and progress to definition of requirements, exploration of
      possible solutions, and creation of conceptual designs for new or improved products. In
      this phase, all good ideas are given an opportunity for evaluation and possible application.
      In the real world of pragmatic, business-driven investments, products are most often devel-
      oped according to market demands and the marketing strategies of the enterprise. Custom-
      er demands evolve in response to product innovation, and technologies are developed to
      overcome technical challenges and provide new capabilities to meet user needs.
     Design – The design stage of the product life-cycle translates requirements into detailed
      plans and product definition data from which products can be made. In today’s prosthetics
      environment, design often starts with a standard structure and adapts that structure to meet
      the needs of the user. However, to the researcher, design means translating creative ideas
      into solutions that can better serve those needs. Design is also the stage of product devel-
      opment where reality must be directly addressed. The realities of process capability, mate-
      rial properties and resource availability, skills, and other factors all go into the determina-
      tion of the best product design.
     Production – This is the stage of the life-cycle where product designs drive the manufac-
      turing and fabrication processes that deliver products. For orthotics and prosthetics, pro-
      duction typically involves the manufacture of standard components and forms, assembly of
      those elements into the desired types of devices, and creative adaptation and customization
      of the devices to meet the needs and wants of the individual user.

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     Support – The post-delivery stage of the product life-cycle is unique for orthotic and pros-
      thetic devices. The shape and configuration of residual limbs change hourly, daily, and
      over time, resulting in the need to “settle” for best fit, compensate for changes, and occa-
      sionally to upgrade the devices. Maintenance and adjustment are a regular part of the sup-
      port challenge, which often results in long-term, close relationships between user and prac-
The current state for product life-cycle management in orthotics and prosthetics can best be char-
acterized as progressing although many challenges remain. While integrated product and pro-
cess development and automated manufacturing are the usual goals for most products, orthotics
and prosthetics is still practiced as an art. The production of these devices is very similar to oth-
er general production operations, with off-the-shelf components assembled into the final device.
                                                  However, the fit is critical, and the “fit critical”
                                                  components usually require intense interaction
                                                  between the prosthetists and the user as shown in
                                                  Figure 2-2, Perhaps the most visible of these
                                                  components, particularly with wounded soldiers,
                                                  is the socket for lower-extremity amputees.
                                                  Computer-aided design and manufacturing
                                                  (CAD/CAM) has made significant inroads in the
                                                  creation of sockets, but there are usually two dis-
                                                  tinct phases. The first is the production of an ini-
                                                  tial fitting or temporary fit socket, and the second
                                                  is the production of the actual socket that will be
                                                  used over the long term. CAD/CAM is used
                                                  mainly to create the temporary fit-socket, but not
                                                  the actual socket. The result is that fitting is still
                                                  manually intensive and expensive. Further inte-
                                                  gration and automation are needed to reduce the
                                                  cost and time of this process.
                                               While technology is the intended focus of this
                                               roadmap, it cannot ignore business, regulatory.
Figure 2-2 This child’s orthotic indicates the In fact, the workshop participants strongly voiced
amount of hand crafted customization re-       the opinion that technology issues paled in com-
quired for proper fit.                         parison to the business barriers. The recurring
                                               theme in the discussion centered on the concept
that reimbursement regulations support selling the most expensive existing product that can be
produced – instead of flexibly providing the best service that the user can receive. Several fac-
tors contribute to this problem:
     Insurance companies reimburse by code and payment schedules which makes the orthotics
      and prosthetics environment far more like product sales than supplying medical services.
      Therefore, flexibility in provision of devices and services to assure life-cycle support may
      not be covered. These needed services include special features, gait assessments, fittings,
      and adjustments.

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     A lack of standard terminology causes confusion across the community. The languages
      used by practitioners, research organizations, and insurance companies are not consistent.
     As is the case with all areas of insurance, coverage and payments vary by provider. Medi-
      care guidelines are used as references and standards for comparison. Several states have
      adopted parity legislation to assure a reasonable level of coverage for orthotic and prosthet-
      ic devices.
The observation was made that standards for the industry do not exist. However, the Interna-
tional Standards Organization (ISO) does have an extensive list of standards for orthotics and
prosthetics. It is more likely that existing standards are neither well understood nor applied, and
contain voids in the standards set.

Figure 2-3. The present product realization cycle for prostheses uses advanced technology, but
without a fully integrated approach. Further automation is needed to reduce the cost and time of
the design and fitting process, and eliminating the two-step process is a realistic goal.

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The final characteristic of the current state is an important one. The Certified Prosthetist
Orthotist (CPO) national test has not been maintained to reflect changes in technology. The re-
sult is that the education system and the certification to practice do not support the knowledge
supply chain needed to ensure that users receive the best possible care.
Many encouraging developments in orthotics and prosthetics do point to a better future. While
osseointegration is being practiced in some countries and documentaries about future “bionic
people” may create unrealistic expectations, programs such as DARPA’s Revolutionizing Pros-
thetics project are exploring advances to deliver the future utility needed to provide full quality
of life for prosthetics users.
2.1.1 Innovation and Conceptualization
The innovation process has two components. The first is the development of new ideas and new
products; and the second is engineering the best fit and function that can be provided by availa-
ble devices.
Innovation in the development of new products takes place in multiple forums. Research institu-
tions invest in advancing the edge of the art with new devices, materials, and concepts. Users
innovate with their application, and many of them become engaged in the profession as research-
ers, manufacturers, and advocates. Much of the innovation in orthotics and prosthetics comes
from the users.
Modeling and simulation are powerful tools for innovation and conceptualization, but the ability
to completely and accurately model detailed concepts for evaluation does not exist. Present sys-
tems focus mainly on device dimensions and topography. Anatomical modeling that includes the
viscoelastic properties of the residual limb, physical variations throughout the day, long-term
trends due to weight and environment changes, atrophy of the residual limb, and other factors
impact the fit and function in ways that today’s models cannot handle well.
As is the case in most fast-moving areas of technology, a disconnect exists between the real-
world practitioners and the “professional innovators” in the research community. This gap is
probably less pronounced in the prosthetics field due to its close coupling of art and science.
Many universities and research institutions are part of, or are partnered with, institutions that di-
rectly serve users. On the other end of the spectrum, many orthotics and prosthetics manufactur-
ers have clinical services integrated on the premises with the development and manufacturing
A strong point made in the workshop was that business factors inhibit innovation. The small size
of the market limits the potential return on investment and constrains the business case for in-
vestment. Government programs are stepping up to support needed R&D. Hopefully, this trend
will promote a stronger sustained investment in the future. Insurance codes seem to support sell-
ing product more than serving the needs of the user, and it is difficult to get new devices ap-
proved for coverage.
The second focus of innovation in orthotics and prosthetics is in fitting the device to meet the
needs of the user. Fitting and service are considered skillful arts that are practiced by prosthetists
worldwide. Even though CAD/CAM systems are making progress, meeting the challenge of
best fit and best service still relies on the skilled artisans who build the final devices and the
prosthetists who assure optimum fit and function.

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2.1.2 Design
Orthotics and prosthetics is not an area with a wide diversity of design requirements. In most
cases, prosthetic designers integrate existing parts to create the desired devices and then engineer
a custom socket. The socket choices are tightly bound, and achieving best comfort and function
for the user is an iterative process. Building a socket begins by creating either a casting or a digi-
tal topology – a set of points that define the geometry. When a casting is made directly from the
residual limb, the next step is to replicate the casting with the right material, the right connection
points, and compensation where needed. The digital mapping can be used to create a cutter path
for machining a test socket directly from the CAD data. In an interim step the technician modi-
fies the design to include attachment points, compensations for heavy wear areas, and other ne-
cessities. This preparatory socket and the prosthetic device can be ready within a few hours. In
many shops, both manual casting and CAD-based design are practiced.
Perhaps the greatest deficiency of the current state of design is the lack of integration. As previ-
ously shown in Figure 2.2, use of CAD/CAM has not significantly reduced the time and cost of
initially creating the socket. As proven in other sectors of manufacturing, the real impact of this
technology comes when models drive the creation of the total design. Present best practices
point to that future state as discussed in Section 2.2.
Design conventions for prosthetic devices are not well-documented, and the design standards
that do exist are not pervasively used throughout the industry. Standards exist for the description
of the residual limbs for both upper and lower extremities, but there appear to be no standards
that extend these descriptions to design conventions.
As is also the case in other sectors of manufacturing, CAD/CAM and modeling functions for or-
thotics and prosthetics use software and tools that are proprietary to the software vendors. In-
teroperability between different systems is limited, and the ability to integrate and share infor-
mation across systems is missing.
2.1.3 Production
Fabrication of prosthetic devices involves small lot sizes and highly customized products. Or-
thotics mirrors prosthetics for special-purpose devices and fitting, but production and marketing
of larger quantities of product also enters into the equation. Arch supports, “boots” for stabiliz-
ing feet and ankles, standard braces for joints, and athletic support devices are a few examples
where the business case supports volume production techniques.
Equipment availability is a significant challenge in small-lot production. Total manufacturing
systems are very expensive, and small production volumes typically cannot justify the expendi-
ture. Hence, many small shops and institutes operate with out-of-date, manual equipment where
state-of-the art, computer-controlled equipment is needed.
In putting together the total orthotic or prosthetic device, standard parts are assembled to create a
device which is then custom fit, by either fabrication or adjustment, for critical features such as
brace length or socket fit. The components that make up the devices are readily available from a
number of sources, and a prosthesis purchased from one vendor may have components from sev-
eral vendors. Offshore competition is a significant threat to U.S. orthotic and prosthetic manu-
facturers. As is true for many products today, major competitors in low-wage countries produce
parts and “knockoffs” at prices with which U.S. firms cannot compete.

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A major production challenge, specific to sockets but also relevant for other devices, is elimina-
tion of the need to create a test fit product before producing the “real” prosthesis. The ability to
accurately model the needed geometry, adjust for best fit based on accurate models and data, and
produce with the best materials and processes is required to eliminate the need for an interim de-
The final issue for the current state of product life-cycle management is the use, or lack thereof,
of intellectual property. It is the belief of the workshop participants that significant advances be-
ing made in the research environment are not moving to deployment and commercialization.
Business issues such as liability and small market size are seen as the key barriers in this area.
2.1.4 Support
The most compelling issue related to support is that insurance companies pay for the product, but
may not pay for its support. Hence, the downstream needs for service and repair often have to be
covered in the initial sale. This creates problems for everyone involved. The manufacturers
must be cost-competitive, so the estimates for support are cut close, which jeopardizes the objec-
tive of ensuring very best outcome for the user.
As orthotics and prosthetics technology becomes more sophisticated, the support requirements
increase. Traveling to a research center for evaluation and fitting may not be a challenge, but
receiving adequate support can be. The training and availability of staff to support the more ad-
vanced products is a deficiency worthy of attention.
Access to support for any prosthesis is limited in rural areas and for those without insurance or
other financial resources. There are excellent programs that provide help, however. The Barr
Foundation in Boca Raton, in concert with the Barr Foundation Amputee Assistance Fund, pur-
chases prosthesis for those in need. The Institute of Advanced Prosthetics in Lansing, Michigan
provides services to more than 200 care centers in 29 states and the District of Columbia. The
Prosthetics Outreach Foundation in Seattle serves national and international users with special
needs. While such organizations provide excellent and extremely valuable service, access is still
an issue, and the challenge remains.
Training of orthotics and prosthetics professionals and the currency of that training is an essential
element of life-cycle support. Distance learning, internships, and cooperative education and
training programs address this need. The Center for International Rehabilitation supports re-
search, development, and distribution of orthotics and prosthetics and provides comprehensive
training programs for those who provide rehabilitation services.

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         Technical Barriers
                                                   State of Practice                     Emerging Best Practices
         and/or Deficiencies
Applicable to All Product Life-Cycle Categories

 The path from idea, to concept, to      Conceptualization, design, manu-           CAD/CAM tools are gaining ac-
  product, to supported product is not     facturing, and product support are          ceptance in O&P design and
  integrated and connected                 often supported by different organi-        manufacturing
                                           zations without critical interconnec-
 Regulatory limitations for reim-        Payment is made based on prod-
  bursement are based on limited           ucts sold; the incentive (and often
  markets and support selling existing     the reality) is to sell products with
  products – not solving problems          most advantageous payments
 There are few standards for the         Some standards exist – such as             Industry gradually moving to open
  O&P industry                             size of screw connections, but they         systems
 There is no independent testing          vary by manufacturer and region
  body; access to users limits testing    For most devices, systems and
  opportunity                              support are vendor-specific
 Lack of interoperability of standard    ISO has some standards in pros-
  systems and across company com-          thetics and orthotics
 Missing outcome measures.               Standard solutions are applied by          Manufacturers have prosthetists
 Performance goals and limitations        the prosthetist in concert with the         on their staffs and work closely
                                           user. There is little linkage and           with users in a best solutions
  are not well defined
                                           quantification of the requirements to       partnership; however, geography
                                           best solution.                              limits user access
                                          The sale is often the beginning and
                                           end of the relationship
 Education and testing, e.g. national    Educational institutions are meas-         Universities and institutes are
  CPO certification, is based on old       ured by success in achieving certifi-       engaging students in research
  technology (1950s-1960s)                 cation, so the educational structure        that exposes them to the emerg-
                                           supports old technology and does
 Employers want flexible employees        not adequately prepare students for
                                                                                       ing technologies
  with broad understanding while spe-      advanced applications
  cialization is needed for true user
  care                                    Testing still lags the state of the art

 “Discovery Channel” bionic man          The survival rates of the general          DARPA programs show promise
  vision creates expectations that         population and of those wounded in          for improved and revolutionary
  cannot be realized – leading to in-      combat adds incentive for improved          solutions; advanced implantation
  sufficient funding for a perceived       prosthetic care. Funding in some            is available in some countries
  “solved problem”                         cases is increasing.
Innovation and Conceptualization

 Modeling systems that allow evalua-     Modeling systems are used for cap-         Performance modeling used to
  tion of new ideas are not mature nor     turing geometry, and, mostly in the         optimize device concepts
  broadly available                        research environment, for modeling
                                          Limited use of modeling in concep-
                                           tualization for individual devices
 Prototyping is expensive and            Rapid prototyping techniques used          User innovators are taking the
  build/test of new concepts is often      to create casting molds                     lead in moving creative concepts
  cost prohibitive                                                                     forward – designing/
                                                                                       conceiving “experiences” instead
                                                                                       of devices, based on wants,
                                                                                       needs, and requirements

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          Technical Barriers
                                                      State of Practice                   Emerging Best Practices
          and/or Deficiencies
 Gap between university research            University-based centers perform         DARPA Revolutionizing Prosthet-
  that focuses on concepts and the            research, and also support the de-        ics Project (RPP) partnership
  delivery of working devices                 livery of product to users
                                                                                       RPP 2007, led by DEKA Re-
                                                                                       search and Development Corp.,
                                                                                       will design and fabricate an ad-
                                                                                       vanced prosthetic arm and hand
                                                                                       using the best available technolo-
                                                                                       RPP 2009, led by Johns Hopkins
                                                                                        Applied Physics Laboratory con-
                                                                                        tract to develop an advanced
                                                                                        prosthetic arm
 The business drivers support selling       Off-the-shelf products are the norm  Virtual reality, haptics, nanotech-
  existing product, not innovating new
                                             Product lines change very little; new nologies, intelligent systems, and
  products                                                                              flexible devices are being devel-
                                              and innovative ideas slowly move to
 Very small market size (50,000 in           market
                                                                                        oped and deployed
 U.S. for upper extremities) and the
 high price of market entry limits in-
 vestments in innovation

 Lack of integration of components          Components are added to devices          Variable design – all components
  and functions in design (cosmetic           as opposed to creation of an inte-        driven by engineering equation:
  covers inhibit functionality and ser-       grated design                             power, force, velocity, etc.
 Not unified in an integrated model         “Transfer” of information instead of     Computer modeling used to opti-
  (user, manufacturer, researcher)            seamless integration of all ideas in-     mize design and test designs be-
  that supports requirements-based            to an integrated, requirements driv-      fore fabrication
  design                                      en, response
 Current workforce not prepared for         Companies using advanced tech-           Companies committing to
  technology application, e.g.,               nologies tend to compartmentalize         CAD/CAM implementation and
  CAD/CAM, either for design or sup-          with a few trained experts and mul-       training the workforce for support
  port                                        tiple paths/methods for doing the
 Liability issues inhibit open-             Vendor proprietary solutions domi-       Open source/open architecture in
  architecture hardware design                nate the market                           hardware design – forum for user
                                                                                        innovators to offer personal indi-
                                                                                        vidual solutions.
 Liability issues limit incorporation of    Traditional designs and technolo-        Autonomy in prosthetic function;
  new ideas and emerging technolo-            gies dominate designs                     balancing autonomy and human
  gies                                                                                  command motion
                                                                                       Modular and integrated design
                                                                                       Adaptive design – limbs that
                                                                                       Elimination of diagnostic proto-
                                                                                        type by designing for use

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         Technical Barriers
                                                   State of Practice                     Emerging Best Practices
         and/or Deficiencies

 High cost of total systems limits      Limited market size and custom fit          Mass customization is lowering
  availability of needed equipment          drives high cost of product                costs even for edge-of-the-art
 Foreign competition for component      Many components made in low                 Automation of manufacturing from
  manufacture makes it difficult for        wage countries; strong competition         CAD models offers great potential
  U.S. companies to compete; limits         from European companies                    for offsetting labor costs and in-
  capability                                                                           creasing U.S. market share.
 Lack of integration from CAD to        CAD/CAM becoming mainstream in              Dynamic scanning to CAD repre-
  CAM                                       design and production                      sentation, interactive edits for
                                                                                       structure and connection, directly
                                                                                       to automated programming of
                                                                                       production equipment
 Necessity to build twice:              A diagnostic device built from a            New scanning and manufacturing
   1) Diagnostic devices                    scan or a mold is fitted and tested,       techniques seek elimination of the
   2) The definitive prosthesis             which leads to the prosthetic device       diagnostic processing step
                                            that is then fabricated. Even with
                                            CAD/CAM, a very manually inten-
                                            sive process.
 Lack of integrated models that cap-    Static scans and static models in-          Gait data and other dynamic data
  ture static and dynamic performance       terpolated for dynamic capture,            being integrated into models;
  and requirements; topographic             which leads to loss of performance         modeling of variations and deflec-
  models instead of anatomic models         (static image for dynamic model)           tions included
 Intellectual property ownership of     Intellectual property developed by          No known best practices
  unused processes                          the Government is often unused
 Inaccuracies in duplication – from     Inaccuracies build up from devia-           Design modeling systems drive
  static model to prosthesis                tions and changes in materials, ma-        automated processing
                                            chines, systems, user volume, jigs
                                            and fixtures, etc.

 Support costs not covered by many      Support cost borne primarily by the         Some enlightened insurance pro-
  insurance companies                       manufacturer and built into pur-           viders provide flexible support for
                                            chase price                                prosthetics throughout the life-
                                           Prosthetics coverage still evolving –      cycle
                                            some parts now included in                Medicaid covers prosthetics in all
                                            Healthcare Common Procedure                50 states, with varying coverage
                                            Coding System; some covered by             and stipulations
                                            Medicare; some recognition from
                                            FDA. Veterans Administration has          Several states have passed pros-
                                            specific prescription criteria; some       thetic parity legislation requiring
                                            studies done by Department of La-          all insurance companies to pro-
                                            bor and industry.                          vide coverage
                                           The relationship of
                                            cost/reimbursement policies to
                                            availability of services requires fur-
                                            ther clarification
                                           Insurance coverage varies for
                                            socket, suspension mechanism,
                                            knee joints, pylon, foot, etc.; reluc-
                                            tant to pay for enhanced features,
                                            evaluations, gait assessments, fit-
                                            ting, adjustments, etc.

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         Technical Barriers
                                                     State of Practice                      Emerging Best Practices
         and/or Deficiencies
 Sophisticated devices demand              The transition from R&D to produc-          Universities working with insti-
  greatly enhanced technological sup-        tion often does not extend to sup-           tutes and affiliated companies
  port                                       port. The R&D side of the compa-             provide a broader and deeper
                                             nies support the emerging products           product life-cycle support system
 Support for rural communities             Location near an advanced insti-            Programs exist to assure care for
                                             tute, clinic, or full-service manufac-       those who are isolated by finan-
                                             turer is critical for excellence in care     cial limitations or location
                                                                                         Barr Foundation purchases pros-
                                                                                          thetic limbs for amputees who
                                                                                          cannot afford them.
                                                                                         Institute for the Advancement of
                                                                                          Prosthetics specializes in O&P
                                                                                          practice management and pro-
                                                                                          vides O&P services to 212 care
                                                                                          centers in 29 states and the Dis-
                                                                                          trict of Columbia.
                                                                                         Prosthetics Outreach Foundation
                                                                                          in Seattle provides U.S. and in-
                                                                                          ternational assistance
 Difficulty in maintaining an adequate     Manufacturer bears cost of educa-           Manufacturers/vendors doing a
  awareness level for education              tion                                         good job in practitioner education
  a. Lack of communication between                                                        a. Distance learning by universi-
     industry and universities                                                               ties and manufacturers, includ-
  b. Timeliness of training and diversi-                                                     ing Center for International Re-
     ty of needs leads to lack of cur-                                                       habilitation
     rent experience                                                                      b. Internships and co-op programs

In the vision of the future for life-cycle management of orthotic and prosthetic devices, every
recipient of an orthotic or prosthetic device will receive the best total solution that restores full
quality of life. Product concepts will be evaluated in an environment that accurately simulates,
in every way, the scenarios that reveal requirements for optimal performance, comfort, and total
life-cycle value. Users will be able to interact with the scenarios to make trade-offs and adapt
the solution to best meet their specific needs. The technology, the business systems, and the cul-
tural issues will all mold together to deliver the best total value for the person most affected.
2.2.1 Innovation and Conceptualization
Vision: The prosthetic experience will evaluate all attributes that impact performance and user
experience for total value optimization, including specific use scenarios for individual applica-
tions such as military applications
Modeling and simulation systems and rapid prototyping systems will enable the complete and
accurate definition of all data that affects the fit and function of the orthotic and prosthetic devic-
es. Modeling of the user experience will include all aspects of performance across various use
scenarios. All attributes related to the solution space will be integrated into conceptual models
and scenarios in which the user can interact and assist in decision-making. The final solution
will be optimized for total life-cycle performance and value.

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Business systems will support this innovation environment. Insurance codes and fee structures
will provide the needed flexibility to make the best solutions available to the user. The modeling
systems will provide the data necessary to assure best value for all stakeholders.
The research and development environment will support innovation for the public good. Funds
will be available to assure that adequate emphasis is placed on orthotics and prosthetics research,
and new intellectual property will quickly find its way to the marketplace.
Major innovations will include intelligent prosthetics as embedded systems that will measure re-
al-time changes in the environment and in the geometry of the residual limb, and adapt to those
changes automatically and continuously. This should dramatically increase the long term com-
fort so vital for lengthy Warfighter missions.
2.2.2 Design
Vision: All product requirements will be formalized into a total digital information package that
completely defines the best solution for the user. The product design will be produced in a con-
current environment wherein technological and manufacturing capability and life-cycle issues
are considered. The resulting design will satisfy all requirements for a product that is produci-
ble, supportable, and cost-effective while returning the fullest possible quality of life for the user.
The orthotics and prosthetics modeling and simulation environment will seamlessly provide
needed information to the design systems at the required level of detail. Design parameters will
be captured from the modeling systems and enhanced for the necessary level of fidelity by the
combined efforts of information systems and human experts. The product design will be devel-
oped in a closed-loop environment wherein process capability, life-cycle issues, affordability,
and other factors are all considered in the product design. The result will be the best possible
solution for the user.
All design perspectives – electrical, mechanical, structural, and others – will be integrated in in-
dustry-common design systems in which data is exchanged without loss of accuracy or the need
for translation. The resulting designs will represent complete product definition packages pos-
sessing all information needed to fabricate and maintain the desired devices.
Unified standards will support the design process and promote a consistent and robust design ca-
pability and practices across the industry. Standard components, interchangeable across vendors,
will allow designers to use the best-in-class components for every application.
2.2.3 Production
Vision: Orthotic and prosthetic products will be manufactured through simplified, standardized,
automated processes that fully satisfy all design requirements and intent for user-specific solu-
tions using standard materials, components, and devices.
In the future, orthotic and prosthetic fabrication systems will produce “lot size of one” products
(specific to the needs of the user) with the efficiency of mass production. Rapid prototyping or
direct digital manufacturing systems will produce usable parts that satisfy all specifications, us-
ing the best materials and achieving optimum material properties. Fabrication processes will be
standardized and automated, resulting in cost and performance breakthroughs.
For the production of device components, U.S. companies will implement systems that produce
the highest quality products with maximum efficiency. New levels of production efficiency will

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mitigate the labor cost advantages of offshore sources, maintaining a sustainable U.S. presence in
orthotic and prosthetic production.
Rapid prototyping and CAD systems that now produce test sockets will give way to systems and
processes that directly produce the final product with the right materials, the right properties, and
the best fit. The highly variable “art “ that now characterizes the orthotic and prosthetic world
will migrate to one based on information and knowledge-based systems supporting automated
2.2.4 Support
Vision: A comprehensive response structure will assure that the needs of the user are met. Reg-
ulatory bodies, insurance organizations, research institutions, medical practitioners, foundations
and charitable organizations, and the orthotics and prosthetics community will mold together in
an infrastructure that guarantees the correct response to the needs of each user.
In the future, a team approach will characterize the orthotic and prosthetic community. The di-
verse roles of the various players will be harmonized. Insurance codes will provide the flexibil-
ity needed to adapt solutions – products and services – to the needs of every user. Information
systems will provide the needed documentation to assure that the solution provided represents
the best investment for both the insurer and the insured. Doctors and prosthetists will work to-
gether in planning and executing each step of the user care experience. This information rich
network will be extended to provide access to all, regardless of location, and the charitable foun-
dations will assist special-needs cases.
Education systems will be maintained at the state-of-the-art, with lifelong learning part of the
experience of every prosthetics caregiver. The testing and certification systems will also keep
current with the state-of-the-art to assure the qualifications of the practitioners.
Assured life-cycle performance will be built into all devices. Sensors will monitor the perfor-
mance of the devices, and monitoring systems will record and report anomalies. “Intelligent
prosthetic devices” will sense the surrounding environment and adapt for optimum fit and func-
tion. Automated adaptation will be coupled with user specifications. For example, instead of
changing devices to shift from walking to running, the device will sense the activity being at-
tempted and will configure itself to support that activity.

As noted in the Current State discussion, the workshop participants made a very strong point that
the major challenges in product life-cycle management are business and cultural issues. While
the latter issues cannot be addressed by DoD technology programs, they are documented here for
awareness of industry stakeholders. Since the primary purpose of this document is to provide
guidance for technology investment, the technical issues and solutions are recorded separately
from the business and cultural issues.
Technology-Based Issues and Solutions
Issue 2.1 Modeling and Simulation Limitations: Modeling and simulation systems do not ad-
equately capture and represent all information needed for optimal orthotic and prosthetic solu-

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    Solution 2.1.1 Complete User Analysis and Model Definition: Define the toolset needed
    for complete analysis of user needs and for modeling and simulation of the solutions based
    on needs and requirements. This includes topographical, geometric, anatomical, and user
    and activity and response (e.g., the gait of the user or activity profiles) models. The toolset
    should support scenario-based conceptual design that allows user interaction to optimize to-
    tal value.
    Solution 2.1.2 Prioritized Models Needs List: Develop a prioritized list of models needed
    to support requirements-based conceptualization. These needs should address short-, near-,
    and long-term activities.
    Solution 2.1.3 Gap Analysis and Filling of Voids: Conduct a gap analysis against the
    needs list to define and better coordinate what is being done and to identify critical voids.
    Leverage existing and new funding to create an integrated program. The gap analysis should
    map existing activities to the identified needs and rate the level to which the activities satisfy
    the needs. Priorities and technology and manufacturing readiness levels (TRLs/MRLs)
    should be assigned to each identified technology need.
    Solution 2.1.4 Scenario-Based and Interactive Conceptual Design: Develop an integrat-
    ed toolset, including knowledge systems and modeling and simulation tools, that will accept
    user data, fully evaluate the requirements, allow the user to evaluate scenarios, interact with
    preferences, and produce a complete set of models for the best conceptual solution.
Issue 2.2 Manual Design with Limited Optimization: Product design for orthotics and pros-
thetics is mostly a manual process and does not consider all life-cycle functions for total value
optimization. Existing CAD/CAM systems only address a small piece of the design-to-
manufacturing solution. Orthotic and prosthetic devices fall into two categories and combina-
tions of those categories. Some components of each are custom-designed; however, in most ap-
plications, the devices are designed and assembled from off-the-shelf components. Design tools
that automate the assembly design and generate assembly instructions would improve both
productivity and quality.
    Solution 2.2.1 Smart Assembly: Provide smart assembly design capability to assist in se-
    lecting the best compatible components and creating the complete product design along with
    all required assembly instructions.
    Solution 2.2.2 Mature CAD Systems for Orthotics and Prosthetics: Mature existing
    CAD tools to support direct download of modeling information to create product designs.
    Include requirements-based design in these tools. Adapt present systems’ ability for input of
    elasticity indices, stress analysis, and other capabilities for orthotic and prosthetic applica-
    tions. Bring the orthotics and prosthetics community together to work with the technology
    suppliers to implement specific new features and capabilities.
    Solution 2.2.3 Model-Based Design Toolset: Develop a toolset with appropriate levels of
    human interaction and automation that use the full set of models that support the best con-
    ceptual designs to produce detailed designs with all documentation needed for production
    and support. Migration to knowledge-based design and full automation should be consid-
    ered in the development of the toolset. Also, the design system should incorporate virtual
    and physical experience to enable evaluation and optimization.

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Issue 2.3 Lack of Active Response to Changing Environments: The current generation of
prosthetic devices do not adapt for best response to their users’ environment or activity.
      Solution 2.3.1 Embedded Intelligent Information Systems: Develop intelligent infor-
      mation systems that sense the environment around them and automatically respond with the
      correct actions instructions to the prosthetic system.
      Solution 2.3.2 Intelligent Orthotics and Prosthetics: Create intelligent orthotic and pros-
      thetic devices that physically adapt themselves to the sensed environment, based on the op-
      timization information. The underlying intelligent control system has five requirements:
        1. Evaluate the environment and provide a sufficient data to fully define the important as-
           pects of that environment.
        2. Analyze the sensed data to determine whether all parameters are within control limits.
        3. Activate devices that achieve and maintain in-control functionality
        4. Evaluate data to determine trends and provide prognostic response to avoid out-of-
           control situations.
        5. Detect and declare any conditions that threaten proper performance.
Issue 2.4 Two-Step Prosthetics Development: Prosthetic fit is currently performed in two
steps. Hence, the impact of CAD/CAM systems to date in reducing time and cost is minimal.
      Solution 2.4.1 Direct Digital Manufacturing Develop a direct digital manufacturing
      (DDM) toolset that uses accurate models to prepare all information necessary to drive the
      DDM processes and that use the best materials for creating useful product, the first time and
      every time. This effort should leverage the excellent work now being done in DDM, includ-
      ing laser deposition, printing jets, and other techniques to produce accurate products from
      the right materials. Specific developments for orthotics and prosthetics needs include:
               Use small-scale winding and tow-placement machines to accurately build composite
               Use the latest in DDM technology for titanium and other special properties materials
                to produce orthotic and prosthetic components
               Systematize the processes for specific applications to lower the cost of DDM.
      Solution 2.4.2 Create Useful Product, First and Every Time: Improve existing design
      and fabrication systems and modify business practices to make the “test part” the one and
      only solution needed for a particular application. This solution also embraces the integration
      of the modeling and simulation, design, and manufacturing processes to assure the best result
      for the user.
Issue 2.5 Lack of Efficiency in O&P Manufacturing Processes: Lean practices and process
automation see limited use, making U.S. component manufacturing vulnerable to offshore com-
petition. The production of standard orthotic products follows the pattern of many manufactur-

 Techniques such as neural net contact systems and other technologies are being used to determine the best placement algorithms and produce
optimized composite structures. The work conducted at the University of Delaware (http://jtc.sagepub.com/cgi/content/abstract/11/6/573 ) is an
example of relevant research. There are several sources for special-purpose composites fabrication machines.

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ing enterprises, but custom orthotics and almost all prostheses are produced as a combination of
manufacturing processes and applied art.
    Solution 2.5.1 Define Companies for Efficiency Analysis and Improvement: Define U.S.
    based orthotics and prosthetics companies that are willing to participate in an analysis and
    upgrading program.
    Solution 2.5.2 Analysis with Target Companies: Conduct a value stream analysis across
    the industry, with site visits and case studies and best practices documented. Provide rec-
    ommendations for both crosscutting and company-specific improvements, with proper pro-
    cedures for protecting proprietary information.
    Solution 2.5.3 O&P Lean Manufacturing Initiative: Create a Lean Initiative program for
    the orthotics and prosthetics industry. Use the study results from Solution 2.5.2 as the foun-
    dation for this activity.
    Solution 2.5.4 Investment in Infrastructure: Coordinate focused investment with tax in-
    centives and matching funds for critical manufacturing equipment and process improvement.
Issue 2.6 Interoperability of Tools and Components: Tools that support the product life-cycle
for orthotics and prosthetics do not interoperate. Modeling and simulation systems, design tools,
and production equipment do not exchange information seamlessly. Standards for component
design are lacking. Hence, the ability to select the best-in-class components from any vendor
and use those components for the best solutions is lacking.
    Solution 2.6.1 Assessment of Existing Standards and Identification of Voids: Provide
    conventions and standards that support the product life-cycle, particularly focused on the full
    electronic, computer-sensible capture of all information required to manufacture and support
    Solution 2.6.2 Product Development Framework: Provide an integrated product devel-
    opment environment wherein modeling and simulation tools, design tools, production
    equipment, and support systems all operate from a common, shared repository of data, in-
    formation, and knowledge.
Business and Cultural Issues and Solutions
Issue 2.7 Missing Business Case for O&P Investment: Business drivers for investing in new
ideas in this sector are missing or are not well-defined. A very small market size compared to
the total healthcare industry makes the business case difficult to define.
    Solution 2.7.1 Outcome-Based Reimbursement: Develop a manufacturers business model
    that supports reimbursement structures based on desired outcomes, users' needs, and/or satis-
    faction rather than the current product sales model.
    Solution 2.7.2 Funding for O&P Business Issues Resolution: Focus and coordinate Gov-
    ernment funding to resolve critical business issues based on the business model, including
    realistic commercialization. .
    Solution 2.7.3 Reimbursement Based on Diagnosis and Outcome: Develop a clinical
    business model reimbursement structure based on service as it relates to diagnosis and de-
    sired outcome.

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    Solution 2.7.4 Coordinate R&D Investment: Consistent with the goals of the business
    model, encourage and coordinate academia and industry R&D (including both privately and
    publicly funded activities) to focus on products and outcomes.
    Solution 2.7.5 Integrated Program for a Stronger O&P investment: Coordinate the re-
    sults of Solutions 2.7.1 through 2.7.4 with improved regulations and rules for reimbursement,
    including uniform insurance policies (perhaps modeled after existing parity laws).
    Solution 2.7.6 O&P Supportive Funding Structure: Create a self-funding structure advo-
    cating orthotics and prosthetics payments and assuring fair and uniform payment. This solu-
    tion may involve the creation of new insurance company policies or major changes to exist-
    ing ones.
Issue 2.8 Difficulties in Moving to Commercialization: Disconnects between goals, ideas, de-
sign, and manufacturing has created a state where opportunities to bring valuable concepts to
market are being missed.
    Solution 2.8.1 O&P Technology and Business Forums: Provide forums to bring research-
    ers, technology providers, manufacturers, and users together for common understanding and
    unified planning.
    Solution 2.8.2 Tax Incentives for User Investment: Provide incentives to support user in-
    vestment in innovative solutions, such as tax credits for purchase of advanced prostheses.
    Solution 2.8.3 Focused Technology R&D: Focus and coordinate research and develop-
    ment activities around consensus goals to migrate innovative ideas to cost-effective, useable
    solutions, including the business strategy and regulatory compliance.
    Solution 2.8.4 Share Government-Funded Intellectual Property: Exploit Government
    “walk-in” rights to assure use of technologies critical to the needs of the public for unused
    Government-funded intellectual property.
    Solution 2.8.5 Funding for Commercialization of Important Concepts: Provide special
    funding to support mining and maturation of the best R&D concepts to prototyped products.
           Provide “Phase III” SBIR funding for moving from commercialization prototypes to
            manufactured products.
           Provide a special emphasis on “Phase III” funding for orthotics and prosthetics.
Issue 2.9 Technology-Ready Workforce: The current orthotics and prosthetics workforce is
not well prepared for advanced technology applications.
    Solution 2.9.1 Funding for Equipment and Training: Provide funding for provision of
    needed equipment and training programs for students and present employees.
    Solution 2.9.2 Lifelong Learning: Provide a lifelong learning career path for orthotics and
    prosthetics practitioners, both within the clinical community and to other career areas.
    Solution 2.9.3 User Training and Support: Extend the function and capability of orthotics
    and prosthetics providers to assure comprehensive training and support for all users. Create
    elements in the orthotics and prosthetics curriculum that enables these professionals to pro-
    vide needed training for users in the use of advanced devices.

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    Solution 2.9.4 Align Education and Certification: Align education and certification pro-
    cess to current available clinical trends/technologies in the market.
Issue 2.10 Design for Outcome: There is a need for design to realize the best user outcomes
instead of designing to create product. This approach is captured in the Technology section
above as Requirements-Based Design, but underlying business and cultural issues must also be
    Solution 2.10.1 Requirements-Based Design: Conduct studies to define a structure for
    care and payment based on requirements-based design focused on user outcome.
    Solution 2.10.2 Standards for Outcome-Based Performance: Develop new standards and
    build on existing standards to which industry will perform, based on classes of application
    and desired outcomes linked to user requirements.
    Solution 2.10.3 Neutral Broker for Validation of Adherence to Standards: Create a coa-
    lition (with adequate funding) to evaluate product performance, develop outcome measures
    for the industry, and validate products based on performance standards.

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The initial draft solutions-level roadmap for Product Life-Cycle Management is presented below.
The rough-order-of-magnitude funding estimates are provided at the “program” level. The
timeframes given assume starts as soon as possible without reflecting the availability of funding
for a given activity.

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Advanced materials applications encompass all aspects of the materials of construction which
must be considered and applied in the design and fabrication of orthotic and prosthetic devices.
Coverings determine external appearance, while interface materials influence comfort. Structur-
al materials affect the strength and overall weight. Materials knowledge, coupled with insightful
design and quality production processes, is applied to create a highly functional, durable, and
comfortable result.
The functional model for this topic (Figure 3-1) addresses the types of devices for which differ-
ent materials must be engineered and applied, as the spectrum of materials involved is far too
broad to address on a material-specific basis.

                        Figure 3-1. Orthotics & Prosthetics Functional Model

The relevant materials belong to many classes including synthetics, metals, polymers, ceramics,
glasses, and composite materials; and natural materials such as polysaccharides, proteins, en-
zymes, and lipids. Regardless of type, the materials used in orthotic and prosthetic applications
have many requirements in common. They must be non-toxic, biologically and chemically sta-
ble, and have sufficient mechanical integrity and strength to withstand physiological loads.
There is a vast array of materials to choose from when designing the optimal orthotic and/or
prosthetic solution for a particular individual, and no one material is the best for all circumstanc-
es. Each individual should be evaluated with careful consideration given to their lifestyle, expec-
tations, and physical characteristics. The orthotist and prosthetist must be knowledgeable about
working with such traditional materials as wood, steel, and leather while expanding their reper-
toire to include advanced materials such as titanium, carbon fiber, and plastics.
Innovative but pragmatic utilization of readily available, naturally occurring, and manmade ma-
terials is a cornerstone for orthotic and prosthetic applications. Reliance on natural materials

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such as wood, leather, wool, and iron has diminished as metal alloys, plastics, polymers, and
composites have come into widespread use for all components. Due to the small commercial
market, orthotics and prosthetics are not significant drivers for new materials development. New
materials and processes are typically first developed for large-volume markets such as aerospace,
automotive, military, and medical. Transfer of materials knowledge from other industries, cou-
pled with innovative application, is the typical path of materials advancement for the orthotics
and prosthetics industry.
Historically, orthotic and prosthetic devices have been external and noninvasive to the user.
However, as medical science has advanced, the trend is toward more internal and invasive medi-
cal procedures and devices. This development, coupled with increasing expectations for return
to full natural functionality, is pushing the limits of current materials. The need for accelerated
materials research and development and faster knowledge transfer is challenging all members of
the orthotics and prosthetics community: materials researchers, academia, manufacturers, profes-
sionals, practitioners, and end users.
Lack of rapid transition of material advances from other disciplines hampers application devel-
opment. The current reimbursement structure amplifies this barrier by not adequately supporting
new materials applications. However, materials technology partnerships are evolving to assist
with technology transfer and awareness of materials capabilities from defense and commercial
R&D to both military and civilian orthotics and prosthetics needs, (e.g., The Composites Consor-
Material solutions developed and applied in isolation from the full system is a major deficiency
across all orthotics and prosthetics applications. Current practices provide solutions for specific
components and specific conditions, with limited consideration of the full limb/
system, and they typically exclude consideration of the full dynamic use environment. The
DARPA Revolutionizing Prosthetics 2007 and 2009 projects are at the forefront of conducting
full system assessments for the shoulder, arm, and hand.
A lack of fundamental materials knowledge (i.e., materials capabilities and processes) is another
key barrier. Long-term studies of life-cycle materials performance do not exist. Hence, there is
little scientific basis for materials selection and application. This knowledge gap results in sub-
optimal use of materials in design and fabrication indicating a major need for improved physical
properties for all orthotic and prosthetic devices. The property list is long, including strength,
oxidation resistance, stiffness modulation, durability, fracture toughness, fatigue resistance,
weight, weight distribution, and weight management. Today, orthotics and prosthetics profes-
sionals use the materials information provided by the material supplier, augmented by their
knowledge and experience but with little direct connection to a scientific basis. Orthotics and
prosthetics professionals are usually not material specialists, and do not have the equipment or
experience to optimize material developments and applications. R&D departments in larger
companies and some materials consortia are initiating more intensive scientific measurement of
the forces encountered (primarily in the sockets area) during dynamic devices performance –
then leveraging this insight to identify materials and properties that best satisfy those require-


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3.1.1 Cosmeses
Cosmeses are coverings for orthotics and prosthetics which primarily give them a more natural
appearance. Degradation from routine usage and age is still problematic for cosmeses. User ex-
pectations are only marginally satisfied by these artificial skins. Concerns include temperature
and moisture sensitivities and UV radiation resistance. Although significant improvements have
been made with newer prefabricated
skins having enhanced durability,
many users still opt for no cosmeses
because the still seem unnatural or,
even worse, impede functionality of
the device. Manufacturing with
stronger and more elastic materials
such as silicone is an emerging best
practice. Promising developments
include self healing, self-diagnosing,
and self-cooling systems that act like
live skin (Figure 3-2) as demonstrated
by the Microvascular Autonomic
Composites research initiative.9 This
team has designed and developed ad-
vanced synthetic microvascular struc-
tural materials and networks that         Figure 3-2. Optical image of self-healing structure after
emulate many of the key responses of      cracks are formed in the coating.
biological vascular systems.10,11
The desire for natural presentation of color, feel, and movement presents a major challenge for
cosmeses. Matching color with a user’s skin including color variations and lack of color change
capability relative to the environment (e.g., suntan) continues to be pursued. Additional defi-
ciencies include the lack of natural “feel” to the touch, with no mimicking of body temperature
and unnatural texture and compressibility. Prefabricated skins are now available with a range of
natural coloring – from two-tone palmar and dorsal colors for the hand 12 to more than two dozen
color variations,13 but they lack fine features (e.g., hair, pores, and wrinkles). Some multi-
component “systems” use two or more materials: a soft undercovering to give shape, covered by
a second material for appearance. Custom skins with near lifelike qualities such as col-
or/variation and hair are available; however, they are expensive, and hand painting requires
manual production – taking approximately 8 weeks and costing from $3,000 to over $10,000 per
While the primary purpose of the cosmeses is to approximate a natural skin to satisfy the user, it
must be done without inhibiting the functionality of the prosthetic – especially at the joints. This
means that the cosmeses must be part of an integrated functional design. Currently, prefabricat-
ed cosmeses are designed and manufactured as general solutions independent of specific pros-


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thetic designs. Custom cosmeses, however, can be highly intimate with prosthetics designs.
Advanced cosmeses development of a fully lifelike and functional result is included as part of a
fully integrated prosthetic solution via the DARPA Revolutionizing Prosthetics 2007 and 2009
projects. One area within the DARPA project receiving focus is development of “skin” with the
properties and functionality to feel heat, cold, and touch. Researchers from Oak Ridge National
Laboratory (ORNL) and NASA are collaborating to develop FilmSkin – a lightweight durable
composite of biocompatible polyimide and carbon nanotubes.14
3.1.2 Liners
Direct contact with the skin presents major biological challenges for liners. They do not ade-
quately accommodate biological issues such as sweating and the resulting odor/hygiene prob-
lems and adverse skin reactions such as ingrown hair and rashes. Some commercially available
gel liners contain oils and moisturizers to help with the skin interface. Emerging improvements
in design and materials for dynamic hygiene issues include platinum curing and embedded silver
threads to deal with bacteria.
Likewise, the inability of a liner to accommodate mechanical interface needs poses significant
problems. Today’s gel materials deteriorate too quickly and must be replaced frequently. The
liner backing can cause skin irritation by bunching, decreased prosthesis functionality, and re-
duced conformance and support. Liners that are extra thick for enhanced conformance may re-
duce stability for standing and movement. Several efforts to improve material capabilities for
better limb conformance are in progress. New products are evolving that customize liners with
variable thickness and shape, integrate a matrix of materials to alter stretching and conformance
characteristics, and use multiple seals along the liner surface to improve conformance and better
distribute loads. Today’s gel liners have much better conforming ability than previous sock-and-
liner solutions. Advanced materials such as silicone, urethane, and thermoplastic polyester elas-
tomer (TPE), with or without fabric covering, are widely replacing the older pelite (closed-cell
polyethylene foam) material. One innovative design uses accordion tubing to allow natural
movement and flex, thus minimizing bunching and pinching.
The lack of detailed scientific data on many aspects of the liner interface, such as effects on tis-
sue and coupling plus insufficient or poor models for the liner and socket interface is a major
problem. Therefore, professional skill and experience, coupled with trial and error, is the current
approach to resolving many liner issues. Sensors for temperature, moisture, and pressure meas-
urements have been introduced to collect fundamental data. The collection of these data points
to the future use of intelligent materials and systems for liners in which the properties are
adapted to the environment.
Also problematic is that the scope and type of an amputation may hinder liner effectiveness.
Current amputation surgeries typically focus on saving as much of the residual limb as possible
rather than supporting the best use of prosthetics. Better education of orthopedic and vascular
surgical specialists about prosthetic requirements is resulting in better materials applicability, fit,
and utility of prosthetics because the limb is better prepared for the optimal prosthetic application.
3.1.3 Sockets
The socket is the most important prosthetic component because of limb interface, conformance,
and weight distribution requirements. However, socket manufacture and materials usage is con-
     Oak Ridge National Laboratory Review, Vol. 40, No. 2, 2007, page 27; http://www.ornl.gov/ORNLReview.

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sidered more of an art than a manufacturing science. There is little industry-wide control and no
industry standards addressing material applications and production processes. Materials finish-
ing and durability vary widely – a critical problem, since the raw edge of delaminating composite
materials can cause failure, chaffing, or cutting. A general lack of materials properties
knowledge and the inability to translate materials performance into optimum design hampers the
delivery of the optimal socket solutions. Sockets may break because materials are used incor-
rectly. Localized experience and “tried and true” practices dominate. Materials selection is usu-
ally up to the local professional and dependent on the relationship of the practitioner with the
manufacturers. The availability may also be limited by the supplier’s specialties. For example,
some facilities provide only thermoplastic sockets; others may provide only composite structures.
Access to a variety of best-practice options and evaluation of emerging materials is characteristic
of all major institutes and of the leading manufacturers.
A key deficiency in the socket arena is the lack of responsiveness to the dynamic user environ-
ment and to the major load-bearing requirements. The problem may not be inherent to the mate-
rials, but rather to the requirement for a structure with a variety of compliances – from hard exte-
rior to hard interior through a soft intermediate structure (e.g., through skin and muscle to interi-
or bone). The residual limb changes throughout the day and over longer periods, but today’s
sockets do not adjust. As a result, socket design, manufacture, and materials considerations are
based on static, not dynamic, measurements. In the current environment, sockets are highly cus-
tomized to accommodate unique load transfers and use a variety of materials, lotions, and other
materials that have not been thoroughly researched for a dynamic environment. Residual limb
static scanning and CAD/CAM to create near anatomically correct contour blanks for better-
fitting sockets and materials application is prevalent. Internet transfer of these scanning data
gives even small and remotely located prosthetic shops access to CAD/CAM capability.
Design and materials applications rely on experience and skill with little direct connection to a
scientific basis. The parameters for materials designs and creation are not well integrated with
the processes that incorporate the materials into the finished prosthetic. Improved testing, meas-
urement, and feedback about the materials environment during prosthetic use are needed to im-
prove materials design. As indicated in other prosthetics areas, the best materials available may
not be used, since orthotics and prosthetics professionals are not material specialists or are not set
up to take advantage of the best options. Emerging best practices include the application of im-
proved modern materials such as braided and laminated carbon fiber, silicone, and thermoplas-
tics for improved contour matching, strength, and affinity for re-shaping operations. Limited as-
sessments are being performed by scientific measurement of the forces encountered by the sock-
et during dynamic performance. This data is then used to identify materials and properties that
best satisfy the requirements.
Sockets, although in use for years and with incremental advancements, still present major issues
with compliance to the limb, cost and time to manufacture, customization and general lack of
accommodating the dynamic movement reality. Osseointegration is a leading candidate as the
future alternative to the traditional socket approach. FDA approval and introduction of
osseointegration in the U.S. within 5 years or less is likely. The practice is already in use in Eu-
rope, using titanium inserts directly into the residual bone.
An important deficiency is the limited use of prosthetic planning in surgical decisions as noted
previously. If the requirements of the likely post-operative prosthesis were used to guide the
amputations, better fit and better results would be achieved. For example, space considerations

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for components and use of bone beveling for improved load bearing capability could be accom-
modated. Today, amputation surgery typically saves as much of the residual limb as possible
rather than supporting the future use of prosthetics. However, there is growing awareness of
prosthetics requirements when selecting and applying surgical techniques. For example, there is
increased recognition of the Ertl procedure (originally developed in 1920) as a good way to per-
form an amputation.15 The Clinical Standards of Practice (CSOP) consensus conference concept
has been promoted in the medical community to bring forth concepts of practice that are not
widely reported in the literature. Postoperative care of the lower-limb amputee is one such area.
Although amputations have been performed for centuries as a lifesaving procedure, the current
protocols for care in some cases may not reflect the complete and active lifestyle of the user.
Therefore, amputation must be viewed as a reconstructive procedure, and the postoperative pro-
tocol must enhance the functional potential of persons forced to undergo this physically and
emotionally difficult surgery.16
Heterotopic ossification (HO), the development of bone in abnormal areas (usually in soft tis-
sues), is a particular complication for leg socket fitting and materials selection. HO has been
perceived as a relatively low-occurrence complication, and the solution has been adaptation of
the socket. However, new research from military amputee cases indicates that HO has a higher
occurrence than thought, and that it can be managed more successfully with follow-up surgery
than with adaptation of the prosthesis.17
3.1.4 Joints18
Providing joints which meet functional requirements and user expectations presents the next ma-
jor material challenge to the orthotics and prosthetics environment. Resistance to heat, moisture,
and body fluids along with age degradation and durability issues are prevalent especially for hy-
draulic actuators, tubing, and seals. Currently, replacements are needed at least every 2 to 3
years or more frequently depending on use patterns. Use of aerospace-grade titanium, polymers,
and carbon composites is increasing as manufacturers replace older steel and plastic materials
with lighter, stronger, and variable properties materials. How best to use these new materials in
the prosthetic environment is the major challenge along with solving cost and processing issues.
Another major challenge is the need to reduce bulk and weight. Weight must be low to reduce
energy expenditure for movement. Bulk must be reduced since the goal for prosthetic joint de-
sign is to stay within the natural size space/geometry envelope. Current practice includes use of
lightweight materials such as titanium, specialty steel, aluminum, polymers, and some basic car-
bon fiber composites. Emerging practice is to use even lighter, more complex materials and al-
loys for components with improved weight-to-strength properties, such as advanced carbon and
polyimide composites coupled with more active electronically managed feedback, actuation, and
There are more standards for prosthetics than orthotics, but not many standards exist for handling
stresses and loads during manufacture. Currently, because much work is by hand, stress risers
are created. In larger facilities, advanced computer-controlled machining in conjunction with

   Ertl Procedure – a New Beginning; www.protesidrottarna.se/inlagg/07janmar/symposiumsammanfattning.htm.
   Heterotopic Ossification Following Traumatic and Combat-Related Amputations Prevalence, Risk Factors, and Preliminary Results of Excision,
   The Journal of Bone and Joint Surgery (American), 2007; 89:476-486. www.ejbjs.org/cgi/content/abstract/89/3/476.
   This area focuses on exoskeleton prosthetic joints as part of an overall prosthetic system. Internal artificial joints such as those used in knee,
   hip, and shoulder replacement surgery were not within the scope of this effort.

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improved designs, better training, and near net-shape methods are alleviating some of the prob-
Achieving natural flexion along with adequate force for lifting and squeezing, and managing
force distribution are “high bar” challenges for prosthetic joints. Current flexure joints are made
of polyurethane but lack the stiffness need for upper-range gripping and lifting. However,
magnetorheological fluids,19 electro-active polymers,20 and mesofluidics21 are being studied for
approximating natural muscle-like performance and control in joint applications.
3.1.5 Limbs
The weight of prosthetics is always an issue, since every ounce of weight requires additional en-
ergy expenditure from the user. While weight reduction is critical for all parts of the orthotic or
prosthetic device, it is even more critical in limbs because the impact of the force (e.g., arm/leg
swing) greatly increases with distance. This is a major design consideration for limbs and termi-
nal devices.
Load-bearing capability also needs improvement. Titanium and carbon composites have effec-
tively replaced wood and iron, but, even with the advanced materials, a user weight of approxi-
mately 275 lbs is the current routine upper limit for widely used materials and designs. Im-
proved titanium alloys, carbon composites, and advanced plastics plus enhanced designs for
larger loads up to 300 lbs or more are emerging. Improved composite structures hold the key for
many future applications.
Functional multi-use capability for different activities
such as adapting to varying terrain or going from the ten-
nis court to the office is an area where there remains much
room for improvement. Currently, many users have mul-
tiple limbs and must switch out the limb to suit the next
activity. The introduction of variable flexion materials in
conjunction with increased range of adaptability of hard-
ware and software such as the Otto Bock C-leg (Figure 3-
3)22 for walking, stairs, running, and gait management is a
best practice.
3.1.6 Terminal Devices
The musculoskeletal complex of the foot and ankle not
only absorbs energy, but also generates more energy than
it absorbs. However, current commercial prostheses are                                        Figure 3-3. The Otto Bock C-Leg
composed of passive materials, and thus can at best only                                      and microprocessor-controlled
partially replace the missing physiological system. There-                                    knees use easy-to-charge lithium ion
                                                                                              batteries with 40-45 hours of power.
fore, active prosthetic components would be required to

   A class of fluids composed of ferrous particles suspended in oil and activated via a magnetic field to go from liquid to near-solid in millisec-
   Polymers whose shape is modified when a voltage is applied to them. They can be used as actuators or sensors. As actuators, they can undergo
   a large amount of deformation while sustaining large forces. Due to the similarities with biological tissues in terms of achievable stress and
   force, they are often called artificial muscles.
   The study and application of the physics and chemistry of fluids at the mesoscopic scale coupled with the use of a flowing liquid or gas in
   various devices to perform functions usually performed by an electric current in electronic devices.

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completely replace the energy generation abilities of the natural limb.23 Applications of electro-
active polymer materials, magnetorheological fluids, and mesofluidics are emerging in advanced
terminal device conceptual designs to address the energy generation concerns.
Compliance management (i.e., full articulation) and modulation is difficult, especially with the
complexities of the human hand. While research continues in restoring the elusive 100% capa-
bility, the state of practice focuses on providing essential functionality from the device in defer-
ence to expensive and/or experimental devices. A project team saw this dramatically illustrated
at a visit to a manufacturer’s site where one of their users demonstrated a myoelectric prosthesis
that had recently been custom fit for him. After the demonstration, he apologized for having to
run to the golf course. As he left the room, he was removing the new arm and getting into his
old device of 8 years – a manual prosthesis. The functionality needs for his golf game were bet-
ter suited by the older technology. This preference does not detract from present research or the
pursuit of the ultimate solution. Recently, the Bio-hand (Touch Bionics i-LIMB hand)24 was
commercially introduced. The DARPA Revolutionizing Prosthetics 2007 and 2009 projects are
pursuing next-generation designs, materials, and capabilities for enhanced hand terminal devices.
Improved reaction of prosthetic feet on a variety of
planes including surface roughness and terrain varia-
bility is a major need. Currently, only limited reaction
ability is accomplished with passive flexion materials
and designs. However, the Ossur proprio-foot (Figure
3-4), which provides for automated detection and ad-
aptation to surface slopes and steps, has been recently
Material strength and durability, especially abrasion
and water resistance, is important for terminal devices.
For foot prosthetics, delaminating of 2-D composite
materials is problematic. Today, easy-to-manufacture
metals such as stainless steel, aluminum, and titanium
and plastics dominate hand terminal device structures.
Foot structures use the same materials plus also carbon Figure 3-4. The proprio-foot provides
composites. Next-generation alloys such as thixo-           for automated detection and adapta-
                                                            tion to surface slopes and steps.
tropic magnesium (a form of magnesium for injection
molding) and more advanced 3-D composite materials are being identified from other industries
for potential application to orthotic and prosthetic needs.
3.1.7 Suspension and Other Systems
The shuttle lock mechanism – made from stainless steel, titanium, and plastics – is a standard
device used for attaching gel liners to the bottom of the socket and has been in use for years.
Suspension sleeves are widely used for attaching prostheses. The sleeve is pulled over both the
prosthesis and a large area of skin to suspend the prosthesis by partial suction. Typical materials
include neoprene, urethane, soft medical-grade silicone, and a nylon/Lycra cover. These materi-

   Transtibial energy-storage-and-return prosthetic devices: A review of energy concepts and a proposed nomenclature, Journal of Rehabilitation
   Research and Development, Vol. 39 No. 1, January/February 2002; Pages 1-11. http://www.rehab.research.va.gov/jour/02/39/1/Hafner.htm.

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als provide strength, elasticity, and optimal adhesion properties. A critical barrier is their lack of
durability. They do not last long and are easily damaged – especially the vacuum seals. Silicone
is becoming widely used for its strength, adhesion, and good seal properties while also reducing
skin irritation effects.
Suspension sleeves rely primarily upon friction and partial suction for “attaching” the prosthetic
to the residual limb, however, two other “attachment” methods use suction and/or vacuum. The-
se two methods are similar in that they rely on an air pressure differential between the ambient
air and a lower air pressure inside the prosthetic socket to hold the prosthetic in place. Suction
suspensions typically rely upon the user to insert the residual limb into the socket and the force
of insertion displaces air thus forming a suction fit. This donning procedure is often assisted
with one-way valves to reduce the insertion effort and more efficiently remove the air. In the
vacuum approach, rather than relying upon the force of insertion, an air removal system (e.g.,
pump) is used to create a vacuum for the suction effect to occur. The vacuum approach is typi-
cally used for users that are not as physically able to use other suspension donning methods.
Whichever suspension method is used, the selection of materials that come in direct contact with
the user’s skins is critical to assure proper attachment of the prosthesis and to minimize irritation
to the skin.

Belts and harness systems are often used as supplemental devices for suspension and attach
around the waist and/or thigh. These systems are adjustable via straps and buckles and use elas-
tic materials.

        Technical Barriers
                                                   State of Practice                      Emerging Best Practices
        and/or Deficiencies
Applicable to All Advanced Materials Categories

 “Material solutions” should not be in     “Material solutions” for specific         Some full system assessments - of
  isolation from the full system             components and specific condi-             shoulder arm, and hand - being
                                             tions; limited consideration of the        conducted via DARPA Revolutioniz-
                                             full limb/system including dynamic         ing Prosthetics 2007 and 2009 pro-
                                             environment                                jects
 Lack of rapid transition of material      Current reimbursement structure           Materials technology partnerships
  advances from other disciplines            doesn’t support trying new mate-           are in place to assist with technolo-
  (i.e., primary advanced materials          rials                                      gy transfer and awareness of mate-
  research is not for O&P, but trickles                                                 rials capabilities of military versus
  in from larger industries – aero-                                                     O&P needs (e.g., Composites Con-
  space, automotive)                                                                    sortium )
 Lack of fundamental knowledge of          Design and materials applications         Limited assessments by scientific
  materials capabilities and process-        rely on experience and skill with          measurement of forces encountered
  es; less than best use of materials        little direct connection to scientific     during dynamic prosthesis perfor-
  in design and fabrication                  basis                                      mance; then used to identify materi-
                                                                                        als and properties that best satisfy
 Need improved physical properties:        O&P professionals use the mate-            those requirements (primarily in
  strength, oxidation resistance, stiff-     rials as provided, with experience
                                                                                        sockets area)
  ness modulation, durability, fracture      guiding the selection
  toughness, fatigue resistance,
  weight, weight distribution, weight

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         Technical Barriers
                                                    State of Practice                    Emerging Best Practices
         and/or Deficiencies

 The protective ability changes and         Newer prefabricated skins have          Manufacturing with stronger and
  degrades with routine usage and             enhanced durability than prede-          more elastic materials (e.g., sili-
  age                                         cessors, but many users still opt        cone) is emerging
                                              for no cosmeses
                                                                                      Microvascular Autonomic Compo-
                                                                                       sites research initiative is develop-
                                                                                       ing synthetic microvascular materi-
                                                                                       als and networks with self-healing
 Mix of cosmeses materials, design,         Prefabricated options are de-           Advanced development of full natu-
  and/or “fit” may inhibit functionality      signed and manufactured as gen-          ral look and synthetic temperature-
  of the prosthesis - especially at           eral solutions independently of          and pressure-sensitive skin as part
  joints (e.g., foundation between            specific prosthetic designs              of a fully integrated prosthetic solu-
  foam cover and underlying compo-                                                     tion within the DARPA 2007 and
  nents sometimes sticky and can al-                                                   2009 projects (e.g., FilmSkin)
  ter the function of the prosthesis)

 Lack of full natural presentation in       Prefabricated skins are now             Custom skins with near lifelike quali-
  color, feel, and movement for mass          available with range of natural          ties – color/variation and hair; how-
  produced options                            coloring, but lack fine features         ever, they are expensive and hand-
 Custom options are costly and have          (e.g., hair, pores, wrinkles)            painting causes low production
  lengthy production times                   Multi-component systems using
                                              two or more materials; soft form
                                              for shape covered by second ma-
                                              terial for appearance

 Liners do not adequately accom-            Some gel liners contain oils and        Improved design/materials for the
  modate biological needs: sweating,          moisturizers to help with skin in-       dynamic hygiene issues (e.g., plati-
  odor/hygiene problems and adverse           terface                                  num curing and embedded silver
  reaction by skin (e.g., ingrown hair,                                                threads to deal with bacteria)
 Scope/type of an amputation may            Amputation surgery focuses on           Better education of surgical special-
  cause difficulty in liner effectiveness     saving as much of the residual           ties (e.g., orthopedics and vascular)
  (e.g., trim line for liner for above        limb as possible rather than nec-        about user and prosthetic require-
  knee difficult to determine. Would          essarily assessing future pros-          ments is resulting in better materials
  like to have room for some outage           thetics. This introduces materials       applicability, fit, and utility because
  but often limb is too short.)               issues as materials are used to          the limb is better prepared for the
                                              compensate for residual limb             best likely prosthetic application.
 Lack of scientific understanding for       Trial and error – O&P professional      Some advanced sensors – tempera-
  many aspects of the liner interface         skill and experience                     ture, moisture/humidity – for testing
                                                                                       and scientific measurement
 Inability of liner to accommodate          Improving material capabilities for     Increased customization using ma-
  mechanical/material interface               better limb conformance – gel lin-       terials with better contour/shape
  needs while in use                          ers improve conforming ability           conformance properties
                                              than sock and liner solutions; sili-
                                                                                      Increased flexibility using accordion
                                              cone, urethane, thermoplastic
                                              polyester elastomer (TPE), with or
                                              without fabric covering, some-
                                              times with silver thread
                                             Older pelite (closed-cell polyeth-
                                              ylene foam) phasing out of use

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         Technical Barriers
                                                   State of Practice                    Emerging Best Practices
         and/or Deficiencies

 Socket manufacture is an “art”            Localized O&P experience and/or         Best practices and techniques train-
                                             “tried and true” practices predom-       ing coupled with advanced materials
                                             inate                                    knowledge in larger operations
 Amputation procedures need to             Amputation typically saves as           Improved awareness of prosthetics
  consider anticipated prosthesis fit.       much of the residual limb as pos-        requirements when selecting surgi-
  (i.e., space for components; bone          sible rather than assessing future       cal techniques (e.g., use of the Clin-
  beveling for improved load bearing         use of prosthetics. This introduc-       ical Standards of Practice and in-
  capability)                                es materials issues, as materials        creased recognition of Ertl proce-
                                             are used to compensate for re-           dure as a good way to make a am-
                                             sidual limb conditions.                  putation)
 Heterotopic ossification (HO), the        HO is perceived as relatively low       New research indicates HO has a
  development of bone in abnormal            occurrence complication – requir-        higher occurrence than thought, but
  areas, usually in soft tissues, is a       ing adaptation of the socket             is managed successfully with follow-
  complication                                                                        up surgery and/or adaptation of the

 Lack of responsiveness to dynamic         Sockets are highly customized for       Improved modern materials: braded
  environment and load-bearing re-           unique load transfers and use a          and laminate carbon fiber, silicone,
  quirements                                 variety of materials, lotions, and       thermoplastics for improved contour
 The problem may not be inherent to         other materials not thoroughly re-       matching, strength, and reshaping
  the materials used, but rather with
                                             searched in a dynamic environ-
                                                                                     Limited assessments done by scien-
  trying to build a structure with a va-                                              tific measurement of the forces en-
  riety of compliances (i.e., must go       Use of residual limb static scan-        countered by the socket during dy-
  from hard exterior to hard interior        ning and CAD/CAM to create               namic performance; then used to
  through a soft intermediate - out-         near anatomically correct contour        identify materials and properties that
  side of socket, through skin, mus-         blanks for better fitting sockets        best satisfy those requirements
  cle, to interior bone)                     and materials application                (primarily in sockets area)
                                            Design and materials applications
                                             rely on experience and skill; little
                                             connection to science
 Sockets still present major issues        Potential for introduction of           Osseointegration in use in Europe
  with compliance, cost, time to man-        osseointegration in the U.S. within      (using titanium inserts directly into
  ufacture, customization and lack of        5 years or less with FDA approval        the residual bone as an alternative
  the dynamic movement reality;                                                       to traditional socket)
  osseointegration is a leading candi-
  date to the traditional socket ap-

 Lack of resistance to environment         Depending on use patterns, re-          Some advanced use of aerospace
  conditions, age degradation, and           placements are needed every 2 to         quality titanium, polymers, and
  use durability issues are prevalent.       3 years (or more frequently)             composites
 Too much bulk and weight                  Increased use of lightweight ma-        Increased use of lighter weight-to-
                                             terials: titanium, specialty steel,      strength components (e.g., ad-
                                             aluminum, polymers, and some             vanced carbon and other compo-
                                             basic carbon fiber composites            sites)
 Because much work is by hand,             More standards for prosthetics          Advanced machining, improved
  stress risers are created                  than orthotics, but not many             designs, better training, and use of
                                             standards exist for handling             near net shape methods are helping
                                             stresses and loads during manu-          alleviate some of the problems
 Lack of a “really good” shoulder          Shoulder joints continue to be          DARPA Revolutionizing Prosthetics

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          Technical Barriers
                                                   State of Practice                    Emerging Best Practices
          and/or Deficiencies
  joint                                      problematic                              2007 and 2009 projects are devel-
                                                                                      oping next-generation capabilities
 Microprocessors in joints is a com-       No significant focus on materials
  ponent with material considerations        in this arena
 Natural flexion and generating forc-      Flexure joints made of polyure-         Magnetorheological fluids, electro-
  es for lifting and squeezing is lim-       thane                                    active polymers, and meso-fluidic
  ited                                                                                applications being studied for ap-
                                                                                      proximating muscle-like perfor-
                                                                                      mance and control

 Weight is always an issue – too           Titanium, carbon composites             Improved titanium alloys, advanced
  heavy requires additional energy           have effectively replaced wood           carbon composites, and advanced
  expenditure from user                      and iron                                 plastics
 Load-bearing capability needs im-         ~275 lbs of body weight is the          Newer materials and enhanced de-
  provement                                  current standard limit for widely        signs for larger loads up to 300 lbs.
                                             used materials and designs               or more

 Functional multi-use ability for dif-     Must switch out terminal devices        Variable flexion materials in con-
  ferent activities (e.g., limbs don’t       to suit activity                         junction with increased range of
  adapt well to terrain variability)                                                  adaptability with hardware and soft-
                                                                                      ware (e.g., Otto Bock C-leg)
 Prosthetist preference for materials      Experiential based knowledge            Limited assessment by scientific
  rather than the “best” material for        about materials and forces               measurement of forces encountered
  the user lifestyle/activities; lack of                                              on the limb during dynamic perfor-
  knowledge about forces encoun-                                                      mance, but with limited materials
  tered during those activities                                                       considerations
 Torsion unit issues: elastomer deg-       Each manufacturer selects the           Some studies of torsion units, but
  radation                                   specific materials, but O&P pro-         limited materials considerations
                                             fessionals give little consideration
                                             of materials since they rely on
                                             providers’ expertise
Terminal Devices

 Insufficient energy return and man-       Musculoskeletal complex of foot         Magnetorheological fluids, electro-
  agement                                    and ankle generates more energy          active polymers, and meso-fluidic
                                             than it absorbs; active prosthetic       applications being studied for ap-
                                             components required to com-              proximating muscle-like perfor-
                                             pletely replace the lower limb.          mance and control
                                             However, current commercial
                                             prostheses are composed of pas-
                                             sive materials, and thus can at
                                             best only partially replace the
                                             missing physiological system
 Full compliance (i.e., articulation)      Providing essential functionality       Bio-hand (Touch Bionics i-LIMB
  management                                 predominates over incremental            hand)
                                             and often expensive and experi-
                                                                                     DARPA Revolutionizing Prosthetics
                                             mental, but more functional capa-
                                                                                      2007 and 2009 projects developing
                                                                                      next-generation capabilities for hand
                                                                                      terminal devices
 Reaction of feet on variety of planes     Limited ability with passive flexion    Ossur proprio-foot for automated
  (surface roughness terrain variabil-       materials and designs                    detection and adaptation to surface
  ity)                                                                                slopes and steps

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        Technical Barriers
                                                  State of Practice                    Emerging Best Practices
        and/or Deficiencies
 Material strength and durability          Easy to manufacture metals, plas-      Advanced materials being identified
                                             tics, and composites pre-               from other industries for potential
                                             dominate for key structures             use – aerospace and automotive
Suspensions and Other Systems

 Sleeves do not last long and are          Medical-grade silicone is becom-       Self-repairing capability with more
  easily damaged – especially the            ing widely used in sleeves              durable materials and designs
  vacuum seals
                                            Shuttle lock mechanism standard
 Overall durability, ease of don-           item made with stainless steel, ti-
  ning/doffing, and skin irritation is-      tanium, and plastic
                                            New designs and improved light-
                                             weight and strong materials are
                                             periodically introduced by major
                                             O&P manufacturers for better
                                             suspension performance.

 Some non-materials related items         No materials related information        No materials related information was
  were discussed and captured for          was developed                           developed
  a. Lack understanding of effect of
     prolonged vacuum on residual
  b. Difficulties in proper alignment of
     joint and non-joint components in
     prosthetic to body
  c. Limb length impacts design of
  d. Pin systems allow pistoning (i.e.,
     up and down movement)

In the vision of the future for materials applications, full knowledge of material properties, de-
sign, and manufacturing processes coupled with advanced models of human anatomy and pros-
thetic systems will enable prosthetics that act, feel, and look at least as good as the original natu-
ral limb while providing full or even enhanced functionality.
Smart materials with active microprocessors, direct neural links, and electronics integrated into
the material will enable dynamically compliant, dynamically comfortable, and auto aligning
prosthetics. Materials will be long lasting, bio-tolerant, and facilitate integration into biological
structures and materials to support advanced osseointegration, implantable systems, and integra-
tion with neural networks.
Practitioners in all areas will have easy access to a complete and full understanding of material
properties, designs, and manufacturing processes for all types of components and devices. Mate-
rial models will support all applications and manufacturing processes, enabling evaluation and
optimization to obtain the very best outcome for the person. Standards for materials use, based
on scientific measurement and integrated modeling, will be applied at all levels of the orthotics

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and prosthetics profession. Fundamental materials data will be integrated with static and dynam-
ic anatomical and prosthetic simulations and models to assure the best use of the best materials in
the target application.
Materials knowledge and technology will be readily transferred from orthotics and prosthetics
research and other technology domains. This information will be available for ready access and
use in direct “on-site” design-to-fit and fit-to-design applications.
All orthotics and prosthetics shops will have ready access to materials, techniques and equipment
that allow them to use advanced materials in the most appropriate, consistent, efficient, and cost-
effective manner.
The following provides a visionary materials view by major component type.
3.2.1 Cosmeses
Vision: Future cosmeses will fully replicate the look, feel, and properties of the original body
part while providing robust, lifelong protection of the prosthesis while requiring little or no
The cosmeses of the future will exploit advanced materials to provide a fully natural presentation
with fully lifelike details for color, skin, hair, pores, nails, and sub-skin features. The smart cov-
ering will provide wholly natural feel relative to texture, compression, movement, and tempera-
ture. During movement, the covering retains natural adhesion with no bunching and no interfer-
ence with the underlying prosthetic system. Self-repair capabilities coupled with inherently du-
rable materials allow for fully normal activities and minimal need for maintenance or replace-
3.2.2 Liners
Vision: The liners of the future will be fully transparent to the users and provide a seamless
interface between the prosthesis and the body.
Advanced materials and designs will enable creation of liners that provide an interface that be-
haves as if it wasn’t there while simultaneously being long wearing and self-healing. Excellent
dynamic conformance properties will enable dynamic responsiveness to volume changes during
routine activities. Smooth load transfers at stress points are also provided while maintaining user
comfort for temperature, moisture, friction, and hygiene needs – easily cleaned and odor-free.
3.2.3 Sockets
Vision: The sockets of the future will be extremely lightweight, with lifelong durability, and will
provide a device/body interface that is totally transparent to the user.
This primary interface component will be lightweight yet structurally supportive where and when
needed. It performs as a full residual limb extension in a sleek naturally and dynamically con-
forming manner. No physiological fatigue is amplified even during long and active wear periods.
The dynamically responsive materials and construction provide excellent force transfer. Strate-
gically placed sensors coupled with the science-based material choices for design, production,
and use enable early warning of potential material failure due to fatigue and/or over stress.

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3.2.4 Joints
Vision: Future joints will exploit the unique properties of engineered next-generation materials
to provide full range of motion and load bearing capabilities that enable users to return to full
quality of life.
Future joints will afford their users full 3-D natural motion and ranges of freedom, being dynam-
ically responsive to the environment. Advanced materials of construction will enable load-
carrying capabilities that are no less than natural joints and support self-alignment with terrain
3.2.5 Limbs
Vision: Future materials will facilitate provision of prosthetic limbs that fully replicate – or even
improve on – the performance, weight, and other attributes of the natural limbs they are
engineered to replace.
Advanced materials applications will provide fully natural articulation for both upper and lower
limbs, with appropriate and natural-feeling weight distribution. The materials used will enable
dynamic adjustments to support multiple activities while maintaining overall durability.
3.2.6 Terminal Devices
Vision: Extremely lightweight, strong, and flexible materials will enable cost-effective design
and fabrication of future terminal devices that mimic their living counterparts.
The materials used in terminal devices will support all natural degrees of freedom while provid-
ing fully natural load-bearing and force capabilities. Durability will be excellent for routine eve-
ryday use, with comparable resistance to environmental conditions. Full integration with the re-
sidual limb will be supported for advanced natural neural control, full motion, and integrated
sensor feedback.
3.2.7 Suspensions & Other Systems
Vision: Future advances in materials and device design will eliminate the need for suspension
and ancillary systems in all but the most extreme cases.
Future suspension systems will be long-wearing yet strong and durable. Bio-safe materials will
be used for all skin and transcutaneous applications, and osseointegration will be fully supported.
Smart materials will enable energy scavenging and bio-charging capabilities to support all types
of powered applications.

Key issues identified through the workshop process and subsequent research must be resolved to
realize the vision for advanced materials applications. The issues and supporting solutions either
cut across all of the advanced materials applications area or focus on one (or more) of the com-
ponent sub-areas; the specific coverage is noted in the narrative. The issues and solutions below
provide the framework for the draft roadmap presented in Section 3.4. It should be noted that the
solutions do not represent a definitive plan for resolving each issue, but rather a starting point for
development of more detailed, focused project plans.
The first two issues address the residual limb/device interface, with emphasis on advanced mate-
rials. The first issue is about design and modeling needs. The second is about construction and

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wearing needs. Both acknowledge the shortfalls of understanding and accommodating the dy-
namic nature of the residual limb/device interface, which is a pervasive challenge. The issue is
complex, requiring practitioners to try a design, evaluate the characteristics, and construct a de-
vice with a variety of compliances (i.e., go from hard exterior to hard interior through a soft in-
termediate; from the device exterior through liner, skin, and muscle to the interior bone). The
full effect of the total device including all components – not just the liner/socket – needs to be
factored into the solution. The liner/socket system is the direct interface between the user and
the full prosthetic device. The selection of materials and the construction processes must allow
for geometry, modulus of elasticity, strength, surface properties, weight distribution and man-
agement, and complex dynamic user requirements to ensure a compliant fit.
Current designs are based on a static fitting process with “educated” estimates. Construction is
by hand and uses liners with conforming materials to compensate for anticipated dynamic reality
while preserving the skin and meeting load-bearing needs. A hard socket is fitted over the liner
and is roughly conforming to the limb. The extent of anatomical contours and conformance in
the socket is based on the techniques and materials used to create the socket. The remainder of
the device – limb extensions, joints, and terminal devices – are assembled and connected to the
Limb parameters change with activity not only from movement dynamics, but also from biologi-
cal realities such as swelling and sweating. Additionally, the residual limb basic shape and un-
derlying musculature may change over time from atrophy and/or enhancement due to being used
in a different manner.
Much of the current understanding of residual limb/device interface design and construction is
based on decades-old research and trial-and-error practices, so there is a compelling need to es-
tablish a scientific basis. The significant advances that have occurred over the years need to be
incorporated from basic foundational knowledge areas such as anatomy, biology, physiology,
mechanics and biomechanics, materials science, modeling and simulation, and construction
methods. This integrated knowledge set, coupled with advanced modeling and simulation,
would greatly improve the scientific understanding of interface parameters for static and dynam-
ic modes, and provide a much-improved evaluation process for application of advanced materials.
This knowledge set would also support further materials advances, improve use of existing mate-
rials, and identify better construction methods.
Issue 3.1 Limb/Device Interface Model: An integrated dynamic limb/device interface model
does not exist that is sufficiently robust and accurate to base designs. Advanced modeling capa-
bility is needed to fully address the complex issues of the residual limb/device interface during
dynamic loading and unloading.
    Solution 3.1.1 Model Components and Integration Needs: Identify the components and
    integration needs for an overall limb/device integration model and supporting simulation en-
    Solution 3.1.2 Model Scope and Tools: Define the scope and tools needed for models and
    simulations needed as viewed from the variety of problems to solve – such as biological,
    biomechanics/dynamics, materials, and device mechanics/dynamics.
    Solution 3.1.3 Define Model Parameters: Define the parameters needed to fully assess,
    characterize, and model residual limbs, devices, and materials.

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    Solution 3.1.4 Limb Load Transfer Models and Simulations: Develop dynamic mod-
    els/simulations for device-to-limb load transfer.
    Solution 3.1.5 Gather Knowledge: Gather relevant available data to establish a knowledge
    base for residual limbs, devices, and materials. In the case of materials, find data such as
    materials used in specific environments and information about those environments.
    Solution 3.1.6 Identify and Fill Gaps: Identify and fill in gaps in the knowledge base for
    residual limbs, devices, and materials.
Issue 3.2 Lack of a Temporally and Spatially Variable Liner and Socket: A temporally and
spatially variable liner and socket system – with dynamic characteristics to optimally fit the re-
sidual limb – does not exist. Materials and construction methods need further development to
enable a continually dynamic, optimally fitting, and compliant liner/socket system.
    Solution 3.2.1 Spatially Modulated Materials: Develop materials that provide the ability
    to spatially modulate properties during fabrication. Develop materials with superior 3-D re-
    sponsive conformance abilities. These abilities may be inherent in the materials (e.g., pas-
    sive with no additional external influence) or active with the application of an external force
    such as sensor feedback coupled to direct electrical current, magnetic flux, etc. Additionally,
    the materials may be multi-layered and/or embedded with sensors and circuits to sense and
    manage the conformance characteristics and responsiveness. These materials may be in the
    liner, socket, or both.
    Solution 3.2.2 Temporally Modulated Materials: Develop materials that create the ability
    to temporally modulate device and materials properties during fabrication.
    Solution 3.2.3 Fabrication Processes for Temporal Modulation: Develop fabrication
    processes that support the ability to temporally modulate device and materials properties.
    Solution 3.2.4 Fabrication Processes for Spatial Modulation: Develop fabrication pro-
    cesses that support the ability to spatially modulate device and materials properties.
    Solution 3.2.5 Modulation Control Mechanisms: Develop control mechanisms for dy-
    namic modulation of device and material properties.
Issue 3.3 Lack of Single Terminal Device for Full Requirements: The multitude of a user’s
dynamic requirements cannot be emulated with a single terminal device while maintaining a hu-
man-sized operational envelope. Current terminal devices have neither the degrees of freedom
nor the strength to meet the full range of end user requirements. A user must accept less by ei-
ther adapting to limited essential functionality with one device or switch to another limited de-
vice to perform the range of tasks desired. Additionally, the full-functionality terminal device
must also fit – size- and weight-wise – into the natural foot and hand envelope. The full set of
manual and automated control mechanisms needs to be understood relative to the anticipated
performance parameters in the dynamic environment. The device must also meet the same dura-
bility and environmental exposure requirements as the natural foot and hand.
    Solution 3.3.1 Dynamic System Requirements: Assess dynamic system requirements such
    as degrees of freedom, forces and pressures to be applied, speed of response, etc. for termi-
    nal device activities.
    Solution 3.3.2 Control Requirements: Identify and develop manual and automated control
    requirements for advanced terminal devices.

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        Solution 3.3.3 Sense and Actuate Capabilities: Identify methods to sense requirements
        and actuate dynamic solutions. This includes a focus on active and passive materials needs
        for the defined terminal device requirements.
Issue 3.4 Materials Best Practices: There is a compelling need to identify and share best prac-
tices relative to material capabilities, limitations, and processing techniques. Much materials in-
formation exists, but is not consolidated and channeled for broad use by the orthotics and pros-
thetics community. This lack of fundamental knowledge – from pure materials science to long-
term studies for the community – is seriously impeding progress in materials applications. Lack
of knowledge regarding basics such as weight-to-strength comparisons, oxidation resistance,
stiffness, energy response, durability, fracture toughness, fatigue indicators, and best fabrication
practices is preventing best use of available materials in design and fabrication. Materials focus
areas include nano-materials, bio-materials, and passive and active materials across all orthotic
and prosthetic materials applications.
        Solution 3.4.1 Industry-Wide Assessment of Materials: Perform a definitive industry-
        wide assessment of materials in use and research in progress to create a baseline knowledge
        base similar to the industry survey done in the UK.26
        Solution 3.4.2 Materials Special Interest Group: Establish a materials special interest
        group within the orthotics and prosthetics profession to lead the capture and dissemination of
        knowledge, and conduct an annual materials applications workshop.
        Solution 3.4.3 Automated Knowledge Acquisition System: Develop an automated
        knowledge acquisition system for orthotic and prosthetic materials to increase and maintain
        awareness of material developments.
        Solution 3.4.4 Materials Failure Knowledge Base: Develop a knowledge base with statis-
        tics for failure causes and failure propagation.
        Solution 3.4.5 Materials in Use Knowledge Base: Develop a knowledge base and statistics
        on how and what materials are currently in use in orthotic and prosthetic devices.
        Solution 3.4.6 Interactive Materials Repository: Develop a non-proprietary central repos-
        itory and retrieval environment, support systems, and analysis protocols for the acquired data
        sets for use by orthotics and prosthetics professionals, including methods for updating the
        knowledge base and disseminating updates.
Issue 3.5 Integration with End User Physiology: Methods are either lacking or embryonic for
full integration of the artificial limb with the residual limb and user physiology. With next-
generation prostheses becoming more invasive (such as neural control systems and
osseointegration), the need for biomaterials is increasing. These materials need to perform with
minimal disruption to the body while also reducing and/or eliminating infection inside and at the
skin interface. Several areas need more intensive efforts – with a strong materials focus – to im-
prove integration of the artificial limb with the user. The key areas of need are osseointegration,
neural integration, skin interface, and sensing capabilities.

     Who is Doing What In Industry in the UK: Orthopaedic Devices & Materials Directory 2005 – v1.1;
     www.bitecic.com/NOV_PDF/OrthopaedicIndustryMatrix_JWAFinal_Oct2005.pdf; Who is Doing What Academic Research in the UK: Ortho-
     paedic Devices & Materials Directory 2005 – v2.1; www.bitecic.com/NOV_PDF/OrthopaedicAcademicMatrix_JWAFinal_Oct2005.pdf.

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    Solution 3.5.1 Materials for Neural Tissue Interfaces: Develop materials that are biologi-
    cally stable, with long-term durability, for neural tissue interfaces.
    Solution 3.5.2 Materials for Bone Interfaces: Develop materials that are biologically sta-
    ble, with long-term durability, for bone interfaces (osseointegration).
    Solution 3.5.3 Materials for Skin Interfaces: Develop materials that are biologically sta-
    ble, provide skin irritation control and management, and have long-term durability, for skin
    Solution 3.5.4 Materials for Infection Control: Develop materials and bio-materials with
    enhanced infection control management for all interfaces – neural, bone, and skin.
    Solution 3.5.5 Materials for Sensors: Develop materials that are biologically stable, pro-
    vide sense control and management, and have long-term durability, for sensor applications.
Issue 3.6 Research & Technology Transfer to Field: Too much time – typically, years – is
required to transfer research knowledge to actual practice. Improvements are needed to reduce
this time, not only in making practitioners aware of new developments, but also in providing ad-
vanced education and specific skills training to go from the lab to the bedside so the end user
sees the improvements sooner.
    Solution 3.6.1 Education Requirements: Identify and develop education requirements for
    materials and processes for orthotics and prosthetics professionals.
    Solution 3.6.2 Curriculum: Revise the curriculum for orthotics and prosthetics profession-
    als to include materials and processes.
    Solution 3.6.3 Certification: Revise the certification for orthotics and prosthetics special-
    ists to include materials and processes.
    Solution 3.6.4 Accelerated Knowledge Transfer: Develop faster knowledge transfer
    methods to move materials and processes from lab to patient treatment. Increase ties to re-
    search, practicing universities, manufactures and practitioners – and other industry entities
    specializing in materials, such as aerospace, automotive, and defense.
Issue 3.3.7 Distributed and Customized Fabrication: The current fabrication paradigm is dis-
tributed and customized, leading to less than optimal material selection for applications and re-
sulting in performance below what is available with existing materials and process methods.
While larger orthotics and prosthetics shops have the volume, automation, and advanced soft-
ware to provide consistent material applications, smaller shops use older hands-on methods and
older style materials.
    Solution 3.7.1 Locally Fabricated Materials: Develop materials that can be locally fabri-
    cated efficiently, and develop stock components that are customizable at the customer’s site
    with reasonable process requirements.
    Solution 3.7.2 Materials and Fabrication Learning: Add materials and fabrication as part
    of certification and continuing education.
    Solution 3.7.3 Materials and Fabrication Equipment: Make special materials and fabri-
    cation equipment available to small shops.

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Issue 3.8 Biological Responses and Operating Environment: Advances in orthotics and pros-
thetics are hindered by a lack of biologically responsive prostheses and materials, limited under-
standing of the biological responses to prostheses and materials, and lack of data about the de-
vice operating environment. Science-based understanding is needed regarding both sides of the
biological interactions with prostheses and materials: what are the biological responses to the
prosthesis and materials and what is needed to improve the abilities of the prostheses and materi-
als to respond to biological needs? Fundamental data is lacking about the routine operating envi-
ronment – temperature, humidity, stresses and pressures, forces, etc. – experienced by the pros-
thetic device during use. A fully developed and long-term instrumentation and data collection
and processing approach is needed to resolve this knowledge gap, with a specific focus on under-
standing and improving materials and their applications.
    Solution 3.8.1 Identify Biological Issues: Develop methods to identify biological issues;
    such as: biological flux (blood flow, temperature, skin friction, and bacterial concentration,
    etc.) over various time scales.
    Solution 3.8.2 Smart Fit Sensing Technology: Develop smart fit sensing technology with-
    in the prosthetic for sensing and measuring biological flux.
    Solution 3.8.3 Instrumented Prosthetics: Develop a long-term instrumentation, data col-
    lection, and processing approach for fully instrumented prosthetics to include long-term
    studies coupled with full instrumentation on all components with a special socket focus for
    stress, pressure, flex, temperature, moisture data collection and assessment. This would also
    feed advances in modeling and simulation.
    Solution 3.8.4 Knowledge Base for Pre-Fit Considerations: Develop a generalized
    knowledge base to be used for pre-fit considerations.
    Solution 3.8.5 Specific End User Data Collection: Develop a data collection and correla-
    tion environment that can be applied to a specific end user.
Issue 3.3.9 Cosmeses Shortfalls: Cosmeses fall short across the full set of requirements for du-
rability, cost, producibility, flexibility, and lifelike appearance. Near-lifelike cosmeses can be
produced with significant customized and costly hand operations in low volume. While the ap-
pearance results are impressive, the cost is high and key needs such as durability, producibility,
and flexibility are less than desired. Advanced materials and material processing offer great po-
tential to deliver cosmeses meeting all the desired requirements.
    Solution 3.9.1 Current Cosmeses Offerings: Assess current cosmeses offerings, materials,
    and techniques.
    Solution 3.9.2 Materials for Improvement: Identify potential materials for improved
    Solution 3.9.3 Processes for Improvement: Identify potential processes for improved
    Solution 3.9.4 Automated Production Solutions: Develop automated production solutions
    for high-performance/low-cost cosmeses.
Issue 3.10 Energy Harvesting and Storage Technologies: Increased use of powered and ac-
tive prosthetic components highlights the lack of efficient energy harvesting and storage technol-
ogies for the orthotics and prosthetics arena. As the capabilities of powered and active devices

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increase, so do the energy requirements. Development and application of materials are needed to
support energy harvesting and storage technologies for such devices.
    Solution 3.10.1 Available Energy Technologies: Assess available energy harvesting and
    storage technologies suitable for prosthetic applications.
    Solution 3.10.2 Reduced Energy Options: Assess design and material options that require
    reduced energy to function.

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The initial draft solutions-level roadmap for Advanced Materials Applications is presented below.
The rough-order-of-magnitude funding estimates are provided at the “program” level. The
timeframes given assume starts as soon as possible without reflecting the availability of funding
for a given activity.

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                                   4.0 ELECTRONICS & PROCESSING

The electronics and processing components of prosthetic and orthotic devices27 sense current
conditions, convey what function is desired by the user, and make the device perform that func-
tion. The functional model for this topic area (Figure 4-1) has three sub-elements.

                                    Figure 4-1. Orthotics & Prosthetics Functional Model
 These sub-elements are defined as follows:
          Sensors – These devices monitor some nerve impulse or muscle activity in the user, or oth-
           er physical stimulus such as heat, pressure, or a particular motion. Sensors then transmit a
           signal back to the user or to a motor control mechanism (MCM) to enable operation and
           control of the prosthetic device. Sensors fall into two major categories. Some sensors are
           part of the man/machine interface (passing control impulses to the prostheses, or sensing
           physical information to be passed as feedback to the brain), and some sensors act directly
           as part of the prosthetic device mechanism itself.
          Feedback Technologies – Feedback is a communication mechanism within the sensory
           (neural) system, in which the input signal generates an output response that returns to the
           controlling system to influence the continued activity or productivity of the sensory system.
          Motor Control Mechanisms – MCMs are the cooperating anatomical, neural, and pros-
           thetic systems that initiate and sustain voluntary motor activity. This includes the actuators
           that make a device perform its actions (e.g., move, bend, close to grasp) and the mecha-
           nisms used to control how it operates.
Some prosthetics users remain satisfied with traditional, body-powered devices that have no sen-
sors and depend on visual cues and gross sensations felt through the residual limb. However,
significant advances in sensor and feedback technologies and control mechanisms have enabled
much more comprehensive and natural function of prosthetic devices. The sophistication, accu-
racy, and effectiveness of these technologies and their need to make connections to the user have
grown to the extent that the former amalgam of engineering/ mechanical/ biological technologies

     Electronics and processing functions deal almost exclusively with prosthetic devices.

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applied to prosthetics is now pushing inexorably into the realm of medicine. The resulting con-
flict of provider cultures, standard medical procedures, business and compensation practices, and
users’ timeframe requirements is creating many difficult issues to be resolved in the next few
years – issues magnified by to the many amputations resulting from recent military and terrorism
conflicts. These trauma cases are younger than traditional (often elderly) cases, have higher ex-
pectations of functional performance as an amputee, and want to return to operational condition
as quickly as possible, with some even returning to active military duty.
A widely recognized barrier to realizing the growing potential of neural sensory communication
to achieve high-level prosthetic function is the lack of standard practices for integrating medical
and prosthetics solutions prior to amputation surgical procedures. Medical planning for amputa-
tions should include consultation by prosthetics experts who have knowledge of the interface
needs and capabilities of the user’s future prosthetic devices. The current disconnect often limits
the potential success of prosthetics technologies and amplifies the growing need to closely inte-
grate medicine, biology, and engineering. The jointly made plans must sometimes span a series
of surgeries to treat traumatic wounds and later make additional detailed adaptations for the pros-
thetic device. General practice is not to attempt the complete set of operations at once, given the
possibility of lingering infections or other complications that must be cleared up before the pros-
thetic phase begins.
Another general barrier to overcome is the higher communication requirement, as prosthetic sen-
sors and electronic controls grow ever more computerized and data-intensive. In order to pro-
vide needed data flow in all directions, growing quantities of information must be acquired, fil-
tered, and integrated, such as transmitting user intent, controlling the device, and feedback of de-
vice performance and sensed conditions. Device designers need better understanding of the data
flow requirements for effective, natural communication to and from the user and their device.
The most challenging barrier for man-machine interface sensors today is the lack of direct neural
contact. People normally control their limbs via neural impulses from the brain, through the
spine, branching out to the various peripheral appendages. Conversely, neural sensors in the skin
and extremities pass physical status information back to the brain. In living systems, these two
modes of communication form a complete physiological sensory feedback loop. Systems have
been developed to carry out the two communication functions, but they cannot be fully integrat-
ed because in users, nerves in the missing muscles and joints cannot communicate their relative
The more advanced commercially available devices today use myoelectric sensors pressed
against the skin. Some are precisely located in a roll-on sleeve or sock liner, pick up the signals,
and pass them to the prosthetic device which actuates the desired functions. For example, a user
may learn to activate different muscle areas on his/her residual limb to make different parts of a
prosthetic arm and hand move, flex, and grasp objects. This control is at a gross level, and re-
quires considerable practice for the user to learn to excite isolated portions of muscle fiber.
There is limited, but promising, use of myoelectric sensors involving the rerouting of the residual
neural fibers to alternate positions in the body where surgically implanted sensors pick up the
signals passed by the user’s cortex and activate the MCM. As of now, this is still a very expen-
sive option for general use; neural systems are still not completely deciphered, and many users
are reluctant to have surgical implants.

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Another barrier to progress is the difficulty of achieving robust, high-density integration of mul-
tiple types of sensors. Current use of sensors to give feedback to the user is limited in the variety
of measurable characteristics and in the level of attainable resolution. Typical sensor data may
detect contact, pressure, heat, or cold. An emerging ability is to provide sensors on prosthetic
fingers allowing for texture detection, such as distinguishing rough and smooth surfaces.
Several groups are making progress in developing prosthetic hands with unprecedented manual
dexterity, with one product currently based on myoelectric sensors (the i-LIMB from Touch Bi-
onics) now commercially available. Much farther from commercial reality, the Cyberhand (de-
veloped by a European group led by Paulo Dario28) combines great dexterity with a control sys-
tem driven by the user’s brain signals. The Cyberhand developers plan to incorporate sensory
feedback in their future work, and estimate that commercial availability is 5 to 8 years away.
As prostheses gain more sensors and on-board computational capacity, they can perform auto-
matic control loops, greatly reducing the cognitive burden on the user. This is analogous to au-
tomatic spinal reflex loops in humans, which take care of much of the complex sensing and
adapting done by our hands, feet, and other joints. The C-leg from Otto Bock HealthCare 29 is a
prominent example of a prosthetic that does significant amounts of sensing and computation to
perform automatic gait analysis. Sensors in such prosthetic systems must be very fast and oper-
ate independently in real time within the MCM. Self-contained sensors within prosthetic devices
have much the same barriers and challenges as any other electromechanical device: how to fit
more and faster sensors, with more intelligence, into the smallest, lightest package possible to
integrate with the other electronics and carry out increasingly complex analysis and control func-
Feedback Technologies
Currently deployed prosthetics allow the user to control the device in various ways (e.g., physi-
cal mechanical forces or myoelectric sensors), but although increasing levels of control are pos-
sible, commercially available devices do not provide sensory feedback to the user. There is little
or no direct feedback from the device about conditions adjacent to the prosthetic (e.g. tempera-
ture, surface texture, hardness) or concerning the result of ongoing actions. The user depends
largely on visual clues and to some extent on gross signals felt in the residual limb (e.g. weight
of load or footfall timing).
Some practical methods are used to give approximations of sensory feedback, for example to
communicate tactile contact, pressure, heat, or cold. By transferring the input as vibrations or
electrical stimulations to another skin surface on the body or by auditory signals, the user is then
able to receive the information. Perhaps the most promising current technique is electro-
cutaneous stimulation using many tiny electrodes to stimulate nerves through the skin.
It would be much more effective to have direct stimulation of the neurons that formerly carried
the sensory data from the missing body part with electrodes implanted nearby, as is done in
cochlear implants for artificial ears. A major barrier is that neuroscience has not yet determined
the functions of each nerve fascicle in human nerve bundles, much less how to successfully sepa-
rate the fascicles and reconnect to them to sensors or feedback electrodes. However, the recently
developed Utah Electrode Array30 (Figure 4-2) shows great promise with pill-sized devices that

   Utah Electrode Array to Control Bionic Arm, http://medgadget.com/archives/2006/05/the_utah_electr.html.

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contain arrays of 100 electrodes, each connecting to a small number of nerve fascicles. The sur-
gically implanted device will enable much finer prosthetic control and sensory feedback.

Figure 4-2. The standard Utah array (left) is designed for implantation in the cerebral cortex
while the slanted array (right) is designed for implantation into peripheral nerve.

Motor Control Mechanisms (MCMs)
The MCMs of prosthetics are the cooperating systems (biological, mechanical, and electronic)
that make the prosthesis perform its function for the user. There is increasing use of sensors and
electronics to achieve more sophisticated functionality, and in the case of lower-extremity ampu-
tations, advanced limbs with onboard sensors and computation power (such as the C-leg) have
been widely embraced by users. High-speed sensor data processing enables real-time gait analy-
sis to make automatic adjustments for walking at different speeds, up and down stairs, etc., and
users get locomotion that is much more natural. These systems have the beginnings of hierar-
chical control, in that the leg performs some motor actions automatically, without requiring con-
scious control by the user.
However, the situation is more challenging for upper-extremity amputees, where greater granu-
larity of control and higher-level skills are required, and there is more need for “human in the
loop” interfaces for the high-tech prostheses. Most upper-extremity amputees have not migrated
to newer technologies due to the weight of the limbs, slower reaction speed, and difficulty of use.
Instead, they typically prefer simpler, body-operated hooks that have changed little over the past
100 years.
Energy density is a key problem for powered prosthetics. Batteries cannot deliver power to the
actuators quickly enough for the surge demands made by quick or strong movements. Therefore,
systems are still too slow and heavy, and the need for more sensors compounds the problem.
The second major barrier is inability to provide direct neural interfaces between the human user
and the prosthesis. This requires alternative modes of communication to be set up, often requir-
ing bulky devices and power systems, and sometimes extensive training for the user to become
proficient. There have been demonstrations of targeted nerve innervation in a clinical setting,
and some use of electromyographic controls, but much more development is needed.

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While limited to using myoelectric sensors, the i-LIMB hand (Figure 4-3) from Touch Bionics31
is an impressive development. Billed as the world’s first commercially available bionic hand,
the i-LIMB has five individually powered digits that allow a variety of grips and uses a tradition-
al two-input myoelectric to open and close the fingers. The cosmesis is available as an anatomi-
cally correct match for the user’s appearance, or with semi-transparent skin.

Figure 4-3. The i-LIMB has five individually powered digits that allow a variety of grips and uses
a traditional two-input myoelectric to open and close the fingers.
The Army Research Office is sponsoring promising long-term research on regeneration of four
tissue types. Although the near-term focus is on skin and bone, the longer-term focus is on
nerves and muscles/tendons, so this may ultimately enable neural sensing and feedback.
Another key need is for better, more natural hierarchical controls, so that many actions can take
place automatically at a subconscious control level. Control of current devices uses a variety of
methods to do mode selection and enable adaptive control over different conditions: co-
contraction of different muscles, vocal commands, postural control, even muscle bulging com-
bined with myoelectric pickup to maintain control while adapting the fit of the prosthetic during
the day. However, the better the interface to the user’s brain, the less effort that is required to
operate the prosthetic device.
DARPA has two research programs aimed at producing a fully functional upper limb that re-
sponds to neural control.32 The first program, Revolutionizing Prosthetics 2007, is led by DEKA
Research and Development Corp. Using current, state-of-the-art technology, the goal of the
DEKA project is to create a commercially feasible prosthetic arm that has near-human strength
and appearance. The second program, Revolutionizing Prosthetics 2009, is led by the Applied
Physics Laboratory (APL) at Johns Hopkins University. Here, the goal is a quantum leap in the
advancement of prosthetic devices: a lightweight, natural-looking arm with internal power and
human-like skin that is connected directly to the peripheral and central nervous system so that
users can operate the arm naturally. This is an international effort with groups involved in pros-
thetics, robotics, neuroscience, power systems, sensing, and actuator systems. 33, 34 Prototype


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arms are now being demonstrated (Figure 4-4); the Proto 1 arm (right) is driven by brain signals
to surface-mounted myoelectric sensors. Proto 2 will use implanted electrodes and generate
more sensory feedback to
the user.
Until direct neural
connection of prosthetic
arms becomes possible, a
better understanding is
needed of how to match up
users (who have changing
needs) with the right
prosthesis behavior, and
how to make prostheses
adaptable to users’
individual needs. Learning
methods must be developed
for the mechanics of the
prosthetics to adapt along
                               Figure 4-4. The DEKA arm (left) and the Proto 1 arm (right)35.
with increasing user
capability and changing needs, in order to avoid having the prosthetic device limit the user’s
progress. This does not necessarily imply a steady progression of predetermined control settings.
There may be cases where a user needs different modes of adaptability during the same period.
For example, a user may need limited degrees of freedom (e.g. stiffer movement) when learning
some unaccustomed activities versus having multiple degrees of freedom for other actions (e.g.
to allow more proficiency and more natural flow of the movement).
An important research area relating to user adaptation to the prosthetic concerns neural plasticity,
            How users’ neural structures adapt and learn as they adjust to the prosthetic devices
            How their muscles and tendons change in response to using the prosthetic
            How to have prosthetics adapt to meet the changing needs of the users, and thus avoid
             having the prosthetic limit their progression to regaining more natural function.
Traditionally, many users learn to use one prosthetic and stay with it indefinitely, thereby limit-
ing their opportunity to recover more natural function. Users with sufficient funding and motiva-
tion will use a succession of prosthetics as their recovery progresses and their training and expe-
rience yields more natural control. Researchers hope to better understand this neural adaptation
and incorporate support of smooth neural progression into the prosthetic devices of the future.

     Courtesy of Michael Belfiore in Dispatches from the Final Frontier, http://www.michaelbelfiore.com/blog/2007/08/darpatech-2007.html

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           Technical Barriers                                                                 Emerging Best
                                                       State of Practice
           and/or Deficiencies                                                                  Practices
General Barriers
 Lack of standard practices for integrating     Little to no consideration of          Some amputations planned
  medical amputation surgery with                 subsequent prosthetic issues            with general knowledge to
  prosthetics and knowledge of interface          when amputations are done               accommodate subsequent
  needs of future prosthetic devices                                                      prosthetic possibilities
 Regulatory limitations for reimbursement       Payment made based on prod-            Need more liberal payment
  are based on limited markets and support        ucts sold; the incentive is to sell     schedules focused on per-
  selling existing products – not solving         products with most advanta-             formance and results rather
  problems                                        geous payments                          than products

 Implanted myoelectric sensors and              Upper extremities – surface            Myoelectric signals
  implantable electrodes need to improve           myoelectrics (not implanted),           received through roll-on
  and gain commercial and user                     for example using roll-on               sleeves with integrated
  acceptance in order to move into standard        sleeve technology with limited          electrodes into the sleeve
  clinical practice.                               myoelectric information
                                                                                         Smart, breathable textiles
                                                                                           that identify electrode
                                                                                           position; e.g., multiple
                                                                                           electrodes positioned over
                                                                                           chest region
 Difficulty of multi-sensor, robust high-       “Smart” self-calibrating               Skin/nerve cell/sensor
  density sensor integration                      prostheses                              connections based on
 Technical barrier for tactile sensing          Pneumatic and hydraulic                 information channels that
                                                                                          filter and reduce signals
  includes the reliability, flexibility, and      systems incorporated into smart
                                                                                          from hundreds of sensors
  thermal properties of the interface             prosthetics
                                                                                          per square inch; e.g., tactile
                                                                                          sensor arrays on the palm
                                                                                         Commercially available i-
                                                                                          LIMB hand has 5
                                                                                          individually powered digits
                                                                                          (myoelectric signals); looks
                                                                                          and acts like a real human
 Communication improvements needed to           Lower limbs – basic sensing of         Single sensors on finger that
  be wireless and support a greater array of      forces and movement; kinetic            detect gradients of texture
  variables, better sensing and controls          and kinematics parameters;              such as rough and smooth
                                                  predictive controls                     surfaces
                                                 Biomimetic on-device                   Sensors that detect pressure
                                                  intelligence that can predict the       and multidirectional
                                                  motion such as ankle functions          capability
                                                  (e.g., using gyroscopes and
                                                                                         Pattern recognition and
                                                                                          advanced analysis used to
                                                 Increasingly high-resolution            improve capability and
                                                  sensors for upper- and lower-           performance
                                                  extremity devices
 No capabilities for direct communication to    Limited osseointegration of            Implanted electrodes used
  user’s intact neurons via sensors and           prosthetic to femur and (to lesser      for functional electrical
  electrodes                                      extent) upper limb                      stimulation – some
                                                                                          commercial use (primarily
                                                                                          spinal patients)

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           Technical Barriers                                                                 Emerging Best
                                                        State of Practice
           and/or Deficiencies                                                                  Practices
Feedback Technologies

 Lack of sensory/neural feedback through         Little to no sensing capability in
  skin surface interfaces                          prostheses; use user’s visual
 Need improved information                        clues for feedback
  communication and utility, ability to           Some direct osseofeedback for
  integrate different types of feedback (e.g.,     sensory feedback, e.g., devices
  tactile, visual, auditory)                       that enable users to feel the
                                                   vibration of a vehicle accelerator
                                                   or steering wheel through their
                                                   residual limb
 Neurosurgeons/neuroscience cannot tell          Currently limited to gross            Research to use tiny Utah
  the function of each nerve fascicle.             innervation of whole nerve, but        Electrode Array to connect
  Cannot view at individual nerve fascicles;       needs to be more discrete              to nerve fibers and
  cannot perform nerve separation.                                                        accurately control or receive
                                                                                          feedback using natural
                                                                                          neural connections
Motor Control Mechanisms (MCMs)

 Need better understand of learning              Limiting degrees of freedom for       Teach and playback
  methods for the mechanics of the                 some actions versus allowing           systems
  prosthetics along with increasing user           multiple degrees of freedom for
                                                                                         Commercially available
  capability, to avoid having prosthetic           other actions
                                                                                          hands and partial hands
  device limit user’s progress
                                                  Some users stay with one               with individually
 Limited understanding of neural plasticity,      prosthetic and thus limit their        myoelectrically controlled
  including adaptation/learning how to             recovery of natural function           digits, multiple grips, lifelike
  adjust to prosthetics/muscle tendon
                                                  Users typically use succession         appearance
                                                   of different prosthetics as their     Prototypes of thought-
                                                   recovery and training progress         controlled hand motions
                                                  Hand with a limited number of
 There are no complete tissue engineering        Targeted nerve innervation in         Targeted nerve innervation
  or direct neural interfaces                      the clinical setting; some use of
                                                                                         Army Research Office
 Need improved ability for matching               electromyographic control
                                                                                           sponsoring long-term
  actuators to desired system behavior            Use of force sensor where               research at on regeneration
                                                   position is proportional to the         of four tissue types. Near-
                                                   force but does not have force           term focus is on skin and
                                                   feedback; for example, electric         bone; longer-term focus is
                                                   elbow joints                            on nerve and muscle/tendon
 Insufficient energy storage and supply as      Rechargeable lithium-ion battery       Improved power sources and
  well as power density for actuators.           packs                                  reduction of power needs in
                                                                                        development for advanced
 Better, more natural hierarchical controls      Mode selection: co-contraction        Synergetic controls: control
  are needed, with many actions taking             of muscle, vocal commands and          of whole system (e.g., for
  place at subconscious control level.             pattern recognition used to            walking) versus controlling
                                                   provide multiple degrees of            each of the muscles that
                                                   freedom                                collectively cause motion
                                                  Myoelectric/muscle bulge pickup       Segmented cuff electrodes
                                                   (e.g., from thigh muscles) to          for intact nerves vs. severed
                                                   improve prosthesis fit and             nerves
                                                   enable adaptive control varied
                                                   over time (Catholic University of

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In the vision of the future for Electronics and Processing, the prosthetic device has sufficient
sensory communication so that users can perform activities for daily life fluently and naturally.
The communications encompass command signal acquisition, analysis and control processing,
and feedback transfer to the human to complete the sensory feedback loop. The device is a
“smart prosthetic” that adapts and assumes an increasing level of motor control in concert
with growing user experience and capability. An intuitive, biomimetic operational envelope of
motion allows natural operation with optional enhancement and augmentation as needs
In the future, any person requiring an amputation will have the benefit of multidisciplinary con-
sultations and planning as a standard part of all surgical procedures, thus ensuring optimal prepa-
ration for the best available prosthetic devices and rehabilitation. Although long-term (30 years
or more) projected capabilities may allow complete regeneration of amputated limbs by natural
or biomimetic means, the vision for this roadmap (10-15 years hence) will involve implantation
of or integration with manufactured prosthetic devices.
The medical/prosthetic treatment team will have full understanding of the neural structures in-
volved and how to separate and preserve each nerve structure to the maximum extent possible.
This will enable reconnection of severed nerves to the miniscule electrodes of the expected pros-
thetic configuration. The device may attach directly to remaining bones and joint structures, thus
restoring better symmetry and natural balance to the user. Such osseointegrations will be safe
and effective over the long term due to fully developed mechanical skin interfaces that repel in-
fection and require minimal maintenance.
Whatever the gender, age, weight, or expected activity level of the user,, the prosthetic team will
be able to assemble the appropriate functional modules and customize them to the individual’s
needs, in order to enable natural movement and regain the user’s original strength and range of
Lightweight, high-density power systems with efficient actuators will provide “artificial mus-
cles” that enable natural-looking limbs with weight equivalent to the original biological limb.
The prosthetics will have self-generating power that provides a fast-response energy supply
when needed, and lasts up to a week without recharging.
From new amputees to experienced amputees (as well as those with congenital missing limbs),
all will benefit from “smart” prosthetics. The ability for direct and highly detailed neural inte-
gration of the prosthesis with the user will enable almost perfect sensory feedback loops and
greatly accelerated rehabilitation and recovery of function. New paradigms for sensory analysis,
control, and performance improvement based on feedback will allow a much greater portion of
sensory controls to take place automatically, mimicking spinal reflex loops. These smart pros-
thetics will support amputees with adaptive levels of performance while the users’ own neural
plasticity will allow them to better control and sense feedback from the prosthesis, and to grow
in confidence and capability.

  The workshop group felt it counter-productive to separate the notions of sensors, feedback, and motor control mechanisms into different visions.
Therefore, a single, unified vision is presented in this section.

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Mutual learning will occur because the prosthesis is sensing, adapting, and “learning” the charac-
teristics and parameter settings needed for the user to regain increasing expertise in movement.
As a result, the user will grow continually and dynamically in body strength and functional capa-
bility while using the same device. The result of using smart prosthetics is more smooth and ac-
celerated achievement of user goals and overall improved user outcomes.
Improved understanding of human motor control will enable creation of accurate and robust
mathematical models of natural motion. Counterpart models for prosthetic devices will be com-
posed of functional component models (e.g., sockets or terminal devices) with parameters and
fidelity levels that can be customized to the user’s needs. The component modules and their
many sensors will be used to calculate state variables and control movement. Greater under-
standing and improved techniques will identify the optimization functions and characteristics of
the parameters in the prosthetic. This will include improved analysis of lower extremity motion
for determining symmetric/asymmetric gait optimization.
Better understanding of motion and prosthetic operation will improve filtering and data mining
on the tremendous amount of data generated by the real-time systems and their sensors, enabling
adequate analysis and optimization for real-time control. Compact mathematical models of the
body will support closed-loop control for functions integrated into the prosthetic and not requir-
ing user input. The adaptive devices will have very fast, precise control for both conscious and
unconscious (closed-loop) functions, eliminating temporal lags in selecting the specific mode in
sudden motions. They will also provide improved encoding and decoding of sensory signals, so
that the user can achieve haptic control.
The models will be able to analyze the user’s changing capabilities and adapt the prosthetic de-
vice’s parameters to give more challenging functional options. In this way, the user will not
“reach a plateau” and be limited in the functional capability regained.
Five critical issues limit achievement of the future vision for electronics and processing:
    • Lack of standard surgical practice including prosthetics
    • Inadequate bidirectional information exchange
    • Inadequate control for regaining natural function
    • Inadequate sensing, actuation, energy and power technology
    • Inadequate user adaptation and learning.
Note that the first issue is not primarily technical, but addresses medical and business cultural
practices that must adapt to changing needs. The remaining issues are technical, with the last
one very user-centric. The issues are listed below along with recommended solutions. These
provide the framework for the draft roadmap presented in the next section. It should be noted
that the following does not represent a definitive plan for resolving each issue, but rather a
starting point for the development of more detailed and focused project plans.
The following diagram (Figure 4-5) may be useful for discussing the technical issues. It repre-
sents the generic prosthetic device and its interfaces with the user and the surrounding environ-
ment, and shows where learning or adaptation must occur to optimize prosthetic performance.

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        Natural State                     Device / Appliance
      (e.g. Action Potential)
                                 Decode                   Prosthesis
                                                         State, Actuation


      Human Brain                                   Engineering
        & Body                                      / Prosthesis
                                                                                  Means of transducing or
                                                                                  acquiring relevant neural
                                                                                  or muscular signals

                                          Encode State                            Entity has adaptive,
                                                                                        Entity has adaptive,
                                                                                  variable performance
                                           Information                                  variable performance

       Natural Feedback                                                           Varying number of signals of
                                                                                  different types for each link
       (e.g. Action Potential)

                                                                                 Combination of signals

Figure 4-5. Advances in electronics and processing for prosthetic devices must consider each of the
user/system interfaces with the internal and external environments.

Issue 4.1 Lack of Standard Surgical Practice Including Prosthetics:
This issue is widely recognized as one of the most serious concerns by prosthetists. Solving it
requires development of processes for calling in the prosthetist as part of the accepted standard
surgical planning procedure. It is imperative to get the prosthetist involved at the time of
surgery; as part of standard medical process, this is reportedly starting to happen in the case of
knee replacements. The second solution will integrate standard procedures including prosthetics
considerations into widely used information resources (such as DoD’s Emergency War Surgery),
and assure that surgical training in medical schools includes prosthetics. The third element of
this issue is improving the way that information is used to make surgical decisions. Currently,
the needed information is buried in the literature and cannot be quickly found or used in
emergencies. There is an urgent need in the operating room to provide all of the information
needed to make best decisions – such as background on the type and location of amputation,
photographs to guide the surgeon in evaluating issues and options – with all of this information
readily available and easily navigated for immediate use.
    Solution 4.1.1 Inclusion of Prosthetics in Standard Procedures: Develop standard
    procedures for amputation surgical guidelines which include prosthetics as a facet of the
    standard of care both before surgery and during user rehabilitation and support. This
    solution requires development of standards including prosthetics considerations for every
    common type of amputation. From the standards, develop clinical processes with specific
    guidelines for integration of procedures from the different disciplines.

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    Solution 4.1.2 Education and Information Resources: Integrate the standard
    multidisciplinary procedures into currently used information resources, and modify surgical
    training and standard handbooks to include prosthetics considerations. Make these
    published, standard procedures available as part of hospital certification and service-oriented
    reimbursement processes.
    Solution 4.1.3 On-Line Surgical Decision Support: Develop accessible information
    delivery systems that are available at all venues where needed, including trauma centers and
    other instances where an emergency room physician ends up doing the surgery. The system
    must present the latest standard procedures and guidelines and should also be tailored to
    serve the education and training environment.
Issue 4.2 Inadequate Bidirectional Information Exchange: Current connection of prosthetic
devices to user is generally indirect, indistinct, and not driven by natural motions or neural
signals; substitute signal mechanisms must be learned. This is true for sending control impulses
to the device; receiving feedback signals from the device or the environment back to the human
to affect subsequent actions is usually not even attempted.
Regaining fine control function (e.g., for controlling finger and wrist movements and receiving
sensations), for example, requires many distinct and finely tuned signals. Better understanding is
needed regarding the nature and timing of information flow that takes place within the human
motor control and sensory systems. To achieve this better biological understanding: neurosur-
geons must have better technologies to determine which nerve fascicles control which functions
and for learning how to subdivide muscles. The technology of physically attaching the mecha-
nisms to the human body must also advance to allow robust, long-term performance with mini-
mum maintenance or discomfort.
    Solution 4.2.1 Mechanisms for Efficient Neurotransmission: Develop and improve base
    mechanisms for bidirectional electrophysiological information exchange, including
    myoelectric signals, electromyography, direct nerve connection, more finely targeted muscle
    innervation, and cortical brain interfaces including non-invasive techniques. The focus of
    this solution is to improve the connection between the user’s neural system and the
    prosthetic device’s mechanisms. Targeted technologies may include implanted myoelectric
    sensors, muscle innervation techniques tuned to acquire more information from the user in a
    reasonable manner, or direct tissue regeneration to build neural interfaces.
    Solution 4.2.2 Effective Neurotransmission Systems for Human Use: Implement
    practical, effective, bidirectional neural information exchange systems to achieve natural
    motor control and natural sensory feedback (including tactile sensation) for user. Advance
    basic connection technologies to achieve highly functioning, naturally controlled prostheses.
Issue 4.3 Inadequate Control for Regaining Natural Function: The issue is the need for
control systems that 1) provide enough challenge when first fit, 2) can integrate and adapt based
on feedback from both device and user, and 3) increase the challenge through the end of the
learning process so that the user operates very naturally, with 4) a substantial proportion of
motion being carried out via closed-loop control, not requiring user control.
    Solution 4.3.1 Computer Models of User and the Prosthetic Device for Real-Time
    Control: Develop generic, adaptable models of human performance and neural systems and
    prosthetic mechanisms and performance that capture parameters and measurements from

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    natural motions, e.g., for natural walking and moving around an obstacle. The models will
    be composed of component models with needed fidelity for their function (e.g., a virtual
    model of a knee joint or of prosthetic socket) and will be assembled and optimized to fit the
    user and the prosthetic in use. This solution will analyze massive amounts of sensor data to
    yield a greater understanding and improved parametric optimization techniques for the
    functions and characteristics of the prosthetic.
    Solution 4.3.2 Natural Control of Motions and Forces Based on Inputs from the User
    and the Environment: Using customized models of the user’s body and the prosthetic in
    use, capture continuing status updates and environmental feedback in real time to do
    predictive analysis of motion versus user intent and determine how to control and optimize
    device performance in real-time to achieve that intent safely. Provide mechanisms for an
    adjustable increase in challenge based on user progress, and enable a substantial portion of
    movements to be automatic, not requiring conscious user control. The adaptive devices must
    also provide improved encoding and decoding of sensory signals, so that the amputee can
    achieve haptic control
Issue 4.4 Inadequate Sensing, Actuation, Energy, and Power Technology: There is a
continuing need to increase the number of sensors and types of environmental and user control
input for improving prosthetic function. This creates the requirement for high-density sensors,
sophisticated transducers, and rapid integration and analysis of huge amounts of different types
of information. There is also a need for improved power delivery and long-term energy storage,
plus lightweight, fast-response actuators. Much of this technology can be leveraged from
advances in other sectors.
    Solution 4.4.1 Robust, High-Density Sensor Integration: Develop more comprehensive
    and robust sensors to accept user inputs and to capture, transduce, integrate, and analyze
    increasingly voluminous and variable types of internal and external environmental
    Solution 4.4.2 Improved Energy Technology: Explore and adapt alternative energy
    technologies and higher energy density power supply technologies for use in powering and
    storing energy for prosthetic devices. Focus may include fuel cells, self-generating or
    recharging energy systems, power saving or power scavenging technologies, and integration
    of compact power sources into the prosthetic.
    Solution 4.4.3 Powerful, Lightweight Actuators: Develop new actuator systems that
    deliver quick power with light weight and low noise.
Issue 4.5 Inadequate User Adaptation and Learning: This issue concerns the synergy
between the automated prosthetic, the neural plasticity of the user, and the training regimen that
makes the user work with it to achieve optimum capability. It is imperative to be able to
understand the physical limits and current capabilities of the users and from this basis, to know
how much they can learn (both mentally and with muscle/tendon changes). The focus is not on
building capability into the prosthesis, but rather to create an adaptable ability of the device to
support what they can learn. The paradigm must exploit the plasticity in both – to enable
adaptation of the user to the prosthesis and the prosthesis to the user.
    Solution 4.5.1 Models to Optimize User Adaptation and Neural Plasticity: Develop
    models of user adaptation and learning to use the prosthetic and the associated muscle and

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    tendon changes facilitating neural plasticity, and build training paradigms and protocols that
    can be optimized for different learning situations. The models will analyze the internal and
    external environment and then optimize the use of different learning paradigms. For
    example, a prosthesis should be tuned so that it requires some cognition and adaptation from
    the user. In this way, the prosthetic user will develop the ability to process and generalize to
    new situations.
    Solution 4.5.2 Hardware & Software for Prosthesis Customization: Develop hardware
    and software enabling prosthetists to tune the device to the individual, with suitable coding
    schemes to represent the types of signals that need to be measured and decoded. Include an
    intuitive interface for the prosthetist to work with the system to best fit the user’s current
    needs and for the user to make adjustments as needed for daily activities. Given that every
    amputee has a different set of available muscles and capabilities for controls, the focus here
    is to create devices that will work for a wide range of users by having adaptable performance
    features (such as stiffness of joints or range of motion) with mechanisms for the prosthetist
    and/or the user to modify the associated control parameters and enable the next stage of
    learning progress.

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The initial draft solutions-level roadmap for Electronics and Processing is presented below. The
rough-order-of-magnitude funding estimates are provided at the “program” level. The
timeframes given assume starts as soon as possible without reflecting the availability of funding
for a given activity.

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                                    APPENDIX A
                               WORKSHOP PARTICIPANTS

          Participant                                        Organization
Alvarez, John                    U.S. Air Force
Amirouche, Farid                 University of Illinois Chicago
Andrew, Diane                    Ability Prosthetic System, Inc.
Andrew, Tom                      Ability Prosthetic System, Inc.
Bennett, Brad                    University of Virginia
Bigelow, John                    Johns Hopkins
Choppy, Kristen                  Infoscitex Corporation
Clover, Bill                     Otto Bock
Colvin, Jim                      Ohio Willow Wood
Contreras-Vidal, Jose Luis       University of Maryland
Dignam, John                     Mentis Sciences, Inc.
Fatone, Stefania                 Northwestern University
Fedder, Gary                     ICES, Carnegie Mellon University
Finnieston, Alan                 Biosculptor/Arthur Finnieston Clinic
Ford, Mark                       Ohio Willow Wood
Gilbert, Jeremy                  Syracuse University
Hughes, Gareth                   Zyvex Labs LLC
Hutchison, Janice                Integrated Manufacturing Technology Initiative
Jordan, Sara                     Integrated Manufacturing Technology Initiative
Kuniholm, Jon                    Duke University/Open Prosthetics Project
Martin, David                    University of Michigan
Martin, Jay                      Martin Bionics LLC
Merrell, Mary Ann                Integrated Manufacturing Technology Initiative
Miller, Joe                      Walter Reed Army Medical Center
Nash, Michael                    Institute for Defense Analysis (Defense Logistics Agency)
Neal, Charlie                    Integrated Manufacturing Technology Initiative
Neal, Richard                    Integrated Manufacturing Technology Initiative
                                 Applied Research and Development Institute / South Carolina Research
Norfolk, Chris                   Authority / Composites Manufacturing Technology Center
O’Malley, Marcia                 Rice University

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          Participant                                       Organization
Perez, Jeremiah                Amputee Coalition of America
Player, John                   Infoscitex Corporation
Prusakowski, Paul              American Academy of Orthotists/Prosthetists
Radocy, Bob                    TRS, Inc.
Rolock, Joshua                 U.S. Dept of Veterans Affairs/Northwest University
Roston, Gerald                 Elkins Innovations, Inc.
Rouse, Johnnie                 Texas Assistive Devices/Reactive Metal Corporation
                               Applied Research and Development Institute/South Carolina Re-
Rowe, Charles
                               search Authority/Composites Manufacturing Technology Center
                               Applied Research and Development Institute/South Carolina Re-
Ryan, Marty
                               search Authority/Composites Manufacturing Technology Center
Schmeisser, Elmar              Army Research Office
Scoville, Chuck                Walter Reed Army Medical Center
Shewokis, Patricia             Drexel University
Shreter, Jon                   Allied Orthotics & Prosthetics
Simmons, Layne                 TenXsys, Inc.
Smith, Dennis                  Clemson University
Steele, Rob                    Integrated Manufacturing Technology Initiative
Stowe, Ethan                   Mentis Sciences, Inc.
Tompkins, Michael              Animated Prosthetics, Inc.
Tyler, Dustin                  Case Western Reserve University; Cleveland VA Medical Center
Williams, Dennis               Fillauer Companies, Inc.
Williams, Walley               Liberating Technologies, Inc.
Zahedi, Saeed                  Blatchford-Endolite North America

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                       APPENDIX B
3S - Suction Silicone Suspension: Uses a silicone sleeve with a locking pin to suspend the pros-
AAOP - American Academy of Orthotists and Prosthetists: Founded in November, 1970,
AAOP is a professional society of Orthotists and Prosthetists.
ABC Board Certified Practitioners: Incorporated in August, 1948, practitioners certified by
the American Board of Certification in Prosthetics.
Abduction: Motion of a body part away from the mid-line of the body. Abduction and adduc-
tion are the clockwise and counterclockwise rotations of the leg while the foot is in contact with
the ground.
Abrasion: Wearing away of the skin through rubbing or friction.
ACA: Amputee Coalition of America. Founded in 1986; incorporated in 1989.
Accessible: Easy to approach, enter, operate, participate in, and/or use safely and with dignity by
a person with a disability (i.e., site, facility, work environment, service, or program.)
Acquired Amputation: Limbs surgically removed due to a disease or trauma; generally diabetes,
vascular disease, cancer, bone infection, non-union of fractures, or accidents.
ADA: Americans with Disabilities Act; enacted in 1990.
Adherent Scar Tissue: Scar tissue formed in the healing process which sticks to underlying tis-
sue such as muscle, fascia, or bone.
Afferent: A neuron or pathway that sends signals to the central nervous system or a higher pro-
cessing center.
AK: Above Knee, also referred to as “transfemoral.”
Alignment: Position of prosthetic socket in relation to the foot and knee.
Amputation: Loss or absence of all or part of a limb.
Amputation Types:
        AE                            Above the Elbow (“transhumoral.”)
        AK                            Above the Knee
        BE                            Below the Elbow
        BK                            Below the Knee
        Bilateral                     Both sides (leg or arm)
        DAK                           Double Above Knee, aka bilateral (Bilateral transfemoral)

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        Elbow Disarticulation         Arm at the elbow
        Forequarter                   Arm, shoulder, clavicle and scapula
        Hemipelvectomy                Leg, hip and pelvis
        Hip Disarticulation           Leg at the hip
        Knee Disarticulation          Leg at the knee
        Shoulder Disarticulation      Arm at the shoulder
        Transmetatarsal               Toes and part of forefoot
        Wrist Disarticulation         Hand at the wrist
Anterior: Front, as the front portion of a shoe or foot.
AOPA - American Orthotic and Prosthetic Association: Founded in 1917, a trade association
of facilities (not individuals) that provide orthotic and prosthetic services.
Atrophy: Condition where muscle loss occurs due to lack of use.
BE: Below Elbow, also referred to as “transradial.”
Bilateral Amputee: A person missing either both arms or both legs; a double amputee.
Bilateral Transfemoral Amputee: Both legs amputated above the knee.
Bilateral Transtibial Amputee: Both legs amputated below the knee.
Biomechanics: Applying mechanical principles to the study of how the human body moves.
BK: Below Knee, also referred to as transtibial.
BOC: Board for Orthotists/Prosthetists Certification.
Body Image: The awareness and perception of one's own body relating to both appearance and
Check or Test Socket: A temporary socket, often transparent, made over the plaster model to
aid in obtaining proper fit and function of the prosthesis.
Circumduction: Swinging the hip and leg to the side to allow the foot to clear the floor during
swing phase. This is normally done to compensate for the prosthetic leg being too long.
Congenital Amputee: Individual born missing a limb(s). Technically, these individuals are not
amputees, but are “limb deficient.”
Congenital Anomaly (phocomelia): A birth abnormality such as a missing limb (amelia) or de-
formed limb.
Contracture: Tightening of muscles around a joint which restricts the range of motion. This is
common among brand new amputees after surgery but can and should be avoided.
Cosmesis: Used to describe the outer, aesthetic covering of a prosthesis; refers to the realistic
appearance of the prosthesis, whether a “naturalistic” treatment is attempted.
CP - Certified Prosthetist: A person who has passed certification standards as set by the Amer-
ican Board of Certification in Prosthetics.

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CPO - Certified Prosthetist-Orthotist: A person who has passed certification standards as set
by the American Board of Certification in Prosthetics and Orthotics.
Custom Fit: Fitting an individual with a device made from an image of the individual's anatomy
and fabricated according to the needs of that individual.
Cutouts: A cutout in the anterior (front), and more importantly the posterior (back) side, of a rig-
id carbon-fiber socket to allow a slight “firing" movement of the quadricep and hamstring mus-
cles. These cutouts also serve as a more pliable area of the socket to allow the user to sit on hard
surfaces like a toilet without the prosthesis sliding off the seat. It provides comfort sitting in a
hard seat such as those found in fast-food restaurants. It also allows the area to be massaged in
case of itching, etc. These cutouts also flex slightly to prevent clothes from being creased or torn
against an impliable or otherwise rigid socket. Also referred to as “windows.”
Definitive Prosthesis: A replacement for a missing limb or part of a limb which meets accepted
check-out standards for comfort, fit, alignment, function, appearance, and durability.
Disarticulation: An amputation through a joint, commonly the hip, shoulder, knee, ankle, elbow,
or wrist.
Distal: Further away from the center of the body (your foot is distal to your knee).
Distal Gapping: To determine if there is distal gapping, pull on the locking pin and note the
shape. If the liner puckers or develops concavities, then the liner either was donned improperly
or is too large for the user causing areas that lack contact or exhibit excessive wrinkling.
Doffing: Taking the prosthesis off.
Donning: Putting the prosthesis on.
Dorsiflexion: Related to the ankle joint, pointing the toe or foot upward toward the body.
Dorisflexion and plantarflexion describe the up and down movements at the ankle that enable the
leg to move forward over the foot, pushing the forefoot to the ground.
Durometer: Different density or strength and in this context means it will allow the ankle to
move, bend, or flex more or less.
Dynamic-Response Feet: Store and release energy as the user ambulates. Dynamic-response
feet are much like sophisticated springs that cushion when the heel strikes and use the absorbed
energy to push the foot forward into mid-stance and then into toe-off. The spring action at toe-
off propels the prosthesis through the swing phase of the gait, and the pattern then repeats.
Early Prosthetic Fitting: A procedure in which a preparatory prosthesis is provided for the am-
putee immediately after removal of the sutures. (See IPOP)
ED - Elbow Disarticulation: Amputation of the arm at the elbow. ED is an amputation through
the elbow joint.
Edema: A local or generalized condition in which the body tissues contain an excess of fluid.
Efferent: Indicates a neuron or pathway that sends signals from the central nervous system to the
periphery or to a lower processing center.
Elastic Wrap: Elasticized bandage used to prevent swelling and encourage shrinkage and matu-
ration of the residual limb.

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Endoskeletal Prosthesis: Prosthesis built more like a human skeleton with support and compo-
nents on the inside. This design may have a soft cosmetic cover on the outside.
Energy Storing Foot: A prosthetic foot designed with a flexible heel. It is designed with a
spring that stores energy when weight is applied to it and releases energy when the user transfers
weight to the other foot.
Exoskeletal Prosthesis: A prosthesis that is hollow on the inside with a hard outer surface to
bear weight.
Extension: Extending the leg out; straightening the joint resulting in an increase of angle. Mov-
ing the lower leg away from the back of the thigh.
Extension Assist: A method of assisting the prosthetic to “kick forward” on the swing-through
phase to help speed up the walking cycle.
Extremity or limb: Relates to the arm or leg.
Flexion: Moving the lower leg in, towards the body. In a non-amputee, this would normally in-
volve using the hamstring muscles. The bending of the joint resulting in a decrease of angle;
moving the lower leg toward the back of the thigh.
Folliculitis: Can be caused by a silicon liner that is too tight. See “skin shear.”
Forequarter Amputation (Interscapulthorasic): Amputation of the arm, shoulder, clavicle,
and scapula.
Functional: Designed with the primary goal of controlling an individual’s anatomical function,
such as providing support or stability, or assisting ambulation.
Gait: The range of motion involving how an amputee walks.
Gait Cycle: Begins when one foot contacts the ground and ends when the foot contacts the
ground again. Thus, each cycle begins at initial contact with a stance phase and proceeds
through a swing phase until the cycle ends with the limb’s next initial contact.
Gait Training: Learning how to walk properly with your prosthesis or prostheses.
HD - Hip Disarticulation: Amputation which removes the leg at the hip joint, leaving the pelvis
Heel Strike: The degree of force with which the heel makes contact with the ground during the
walking or running gait.
HP - Hemipelvectomy: An amputation where approximately half of the pelvis is removed.
Hyperextension: Extension of a part of the body beyond normal limits.
IAOP: International Association of Orthotics and Prosthetics. Established in 1992.
Invaginations: A shape or indentation on the residual limb that interferes with total contact of
the silicone liner that cannot be alleviated.
Inversion: Inversion and eversion refer to the motions of the ankle and leg inward and outward
during ambulation.
IPOP - Immediate Post Operative Prosthesis: A temporary prosthesis applied in the operating
room immediately after the amputation.

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KD - Knee Disarticulation or TDK - Through the Knee: Amputation of the leg through the
Kinematics: Observation of recorded amputee motion to determine proper alignment, load-line,
Kinesiology: The study of human motion.
Knee-flexion angle: The range of motion that an artificial knee can bend. Measured in degrees,
the larger the number the better.
L-Codes: Reimbursement codes used in the prosthetic/health care industry to identify what ser-
vices and/or devices were provided. The “L-Code" system is the current method of billing Med-
icare for orthotic and prosthetic services.
Lateral: To the side, away from the mid-line of the body.
LE: Lower extremity
Liner: Suspension systems used to attach the prosthesis to the residual limb and/or provide addi-
tional comfort and protection of the residual limb. These liners may be made of silicon, pelite, or
gel substances.
MCM – Motor-Controlled Mechanism: Any system of the body that initiates and sustains vol-
untary motor activity.
Medial: Toward the mid-line of the body.
Modular Prosthesis: An artificial limb assembled from components or modules, usually of the
endoskeletal type, where the supporting member or pylon may have a cosmetic covering shaped
and finished to resemble the natural limb. (See Cosmesis)
Multiaxis Foot: Allows inversion, eversion, and rotation of foot and is effective for walking on
uneven surfaces.
Myodesis: Muscles anchored to the end of bone; refers to muscles anchored by sutures through
the bone.
Myoelectric Signal: Also called a motor action potential, an electrical impulse that produces
contraction of muscle fibers in the body. The term is most often used in reference to skeletal
muscles that control voluntary movements. Myoelectric signals have frequencies ranging from a
few hertz to about 300 Hz, and voltages ranging from approximately 10 microvolts to 1 millivolt.
Myoelectrics: Literally, muscle electronics. This is a technology used in upper-extremity pros-
thetics and is used to control the prosthesis via muscle contraction using electrical signals from
the muscles to power the prosthesis.
Myoplasty: Muscles anchored to opposing muscles.
Neuroma: The end of a nerve left after amputation which continues to grow in a cauliflower
shape. Neuromas can be troublesome, especially when they are in places where they are subject
to pressure from the prosthesis socket. When possible, the ends of nerves are inserted inside the
bone for protection.
Nylon Sheath: A sock interface worn close to the skin on the residual limb to add comfort and
wick away perspiration.

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Orthosis - Orthotic: An external device applied to limit or assist motion of any given part of the
human body. It is used for protecting, supporting, immobilizing, or treating muscles, joints, or
skeletal parts which are weak, ineffective, deformed, or injured. Singular for a supportive de-
vice; orthoses is plural.
Orthotics: The profession of providing devices to support and straighten the body.
Orthotist: A skilled professional who fabricates orthotic devices that are prescribed by a physi-
Partial Suction: Usually refers to the socket of an above-the-knee prosthesis which has been
modified to allow the wearing of prosthetic socks while wearing the prosthesis.
Phantom Pain: Pain which seems to originate in the portion of the limb which was removed.
Phantom Sensation: The normal ghost image of the absent limb may feel normal at times and at
other times be uncomfortable or painful.
Pin: A locking pin is attached to the end of a silicone liner as part of the suspension system. Pins
are either smooth or serrated and slide into a clutch-like locking mechanism. To remove the leg
a small button is pressed which releases the pin.
Pin-lock: Used to hold the prosthetic limb to the residual limb. Also called a “shuttle-lock" sus-
pension system.
Pin Release Button Guard: Used to protect the release button on a pin-lock system to prevent
accidental release of the pin that is attached to the silicone liner if accidentally bumped.
Pistoning: Refers to the residual limb slipping up and down inside the prosthetic silicone liner or
socket while walking. Sweating exacerbates this situation. This can be solved to some degree
by utilizing a silicone liner that incorporates an internal cloth matrix for greater anti-stretching
stability. Slightly pre-loading the silicone rubber liner when donning also helps.
Plantar: Bottom of the foot.
Plantarflexed - Plantarflexion: Means the toe is pointing down, toward the sole, almost like
pushing the gas pedal down and simulating that position or alignment. Performing a toe-raise is
another example.
Ply: Thickness of the residual limb sock material. The higher the ply numbers the thicker the
sock, i.e. 1-ply, 2-ply, 3-ply, 4-ply, etc. The addition or removal of sock plys are often required
as a result of residual limb swelling or as an amputee gains or loses weight.
Pneumatic/Hydraulic: Used in reference to knee joints; provides controlled changes in the
speed of walking.
Polycentic Knee: Also known as a four-bar linkage knee, this type of knee provides for greater
clearance (hip to toe) when walking. The knee also protrudes less when in a seated position.
(Also known as a four-bar linkage knee.)
Posterior: The back side of the body or part in question, i.e. posterior knee or patellar region.
Prehension: Prehensile, to hold, grasp or pinch.

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Preparatory Prosthesis: An unfinished functional replacement for an amputated limb, fitted and
aligned in accordance with sound biomechanical principles and worn for a limited period of time
to accelerate the rehabilitation process.
Proprioception: The body’s ability to know position and orientation of joints in relation to one
another in static and dynamic environments.
Prosthesis - Prosthetic: An artificial device to replace or augment a missing or impaired part of
the body. In the case of amputees, usually an arm or a leg.
Prosthetic Socks: Socks that provide cushioning and a means to adjust the volume of the socket.
Prosthetic socks are available in several materials including wool, cotton, and synthetics. Sock
thickness is measured by the “ply” rating, most commonly from 1-ply to 6-ply. By varying the
ply number and/or the number of socks worn, user an adjust for changes in the size of their re-
sidual limb. Prosthetic socks should protect the skin against the destructive forces of pressure
and friction in the skin-socket interface, while also absorbing perspiration with a wick-like action
and allowing for ventilation.
Prosthetics: The profession of providing cosmetic and/or functional restoration of missing hu-
man parts.
Prosthetist: A person involved in the science and art of prosthetics; one who designs and fits
artificial limbs.
Proximal: Nearer to the central portion of the body; opposite of distal.
Pylon: A rigid central shaft, usually tubular, that is attached to the socket or knee unit of an
endoskeletal prosthesis and provides a weight bearing support shaft for an endoskeletal prosthe-
sis. Also used to refer to a simple temporary prosthesis. (See shank.)
Quad Socket: A socket designed for an above-the-knee amputee which has four distinctive sides
allowing the muscles to function as much as possible.
Range of Motion: The amount of movement a limb has in a specific direction, at a specific joint,
such as your hip or knee.
Residual Limb: The portion of the arm or leg remaining after the amputation.
Residual Muscles: Muscles remaining after amputation.
Revision: Surgical modification of the residual limb at some later point following the initial am-
Rigid Dressing: A plaster wrap over the residual limb, usually applied in the operating or recov-
ery room immediately following surgery. Used for the purpose of controlling edema (swelling)
and pain. It is preferable, but not necessary, that the rigid dressing be shaped in accordance with
the basic biomechanical principles of socket design.
Rotator: A mechanical unit that is inserted between the prosthetic knee and shin or pylon that
allows an amputee to rotate their prosthetic limb in any direction and sit in a chair with their leg
crossed or cross-legged on the floor. This is also useful when getting into a car, when sitting us-
ing the bathroom, etc.
SACH Foot - Solid-Ankle Cushion Heel: Foot used since the Civil War.
SAFE Foot: Solid Ankle Flexible Endoskeleton.

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SD - Shoulder Disarticulation: Amputation through the shoulder joint.
Sense-of-Feel System: Provides transcutaneous electrical neural stimulation to afferent sense
organs located at the residual limb interface. For example, sensors adhered to the plantar surface
of a prosthetic foot send signals proportional in strength to the amount of pressure applied to cor-
responding electrodes on the residual limb.
Shock Pylon: A prosthetic pylon that dampens the vertical forces exerted on the residual limb.
Shrinker: A prosthetic reducer made of elastic material and designed to help control swelling of
the residual limb (edema) and/or shrink it in preparation for a prosthetic fitting.
Shrinker Prestretch Application Sleeve: A hollow plastic sleeve, open on both ends, which the
elastic shrinker sock is placed over before sliding it over the residual limb. This prevents pain as
the shrinker is easily slid over the swollen limb and the sleeve is gently slid off.
Shuttle Lock: A mechanism that locks the pin attached to the distal end of a liner locking the
residual limb into a socket. Pins can be smooth or notched.
Silicone Liner: Used with pin-lock suspension systems.
Single Axis Foot: Used since the Civil War, this foot is based on an ankle hinge that provides
dorsiflexion and plantarflexion, i.e. toe up and toe down.
Skin Shearing: A line of itchy blisters caused by abnormal pressure, friction, or by shearing of
the skin against “tacky" silicone or plastic. The two most common areas where shearing is no-
ticed when using silicone suspension sleeves are at the proximal liner trim line (top edge of the
liner) and posterior distal aspect (behind the knee area) of the residual limb. Blisters can be
avoided by using a commercially available paint-on film dressing such as MedLogic's
LiquiShield, designed to help prevent skin breakdown.
Socket: The major component of a prosthetic device that the arm or leg rests in. Slang term is
Soft Insert Liner: Cup shaped form which fits inside the socket of a BK.
Soft Socket: A soft liner built into a carbon-fiber prosthetic socket to provide cushioning or to
permit muscle movement and function.
Split Hook: Terminal device with two hook-shaped fingers operated through the action of har-
ness and cable systems.
Stance Control: Friction device with an adjustable brake mechanism to add stability to a pros-
thetic knee unit.
Stance Phase: When the amputee is standing with the foot on the ground with the knee slightly
locked (hyper-extended). The weight distribution is slightly behind the load line so that the knee
is slightly hyper-extended and so the knee won’t buckle.
Suction Socket: A socket designed to provide suspension by means of a negative pressure vacu-
um in the socket; achieved by forcing air out of the socket through a one-way valve when don-
ning (putting it on) and using the prosthesis.
Supercondular Suspension: A method of holding the prosthesis on by clamping on the bony
prominence above a joint, called “condyles.”

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Suspension System(s): The method used to hold the prosthesis on the body. The three primary
methods are suction sockets, roll-on silicone rubber liners with locking pins on the end, and belts.
Swing Phase: Prosthesis moving from full flexion to full extension; usually used in reference to
prosthetic knee units. When the amputee swings the leg forward, from being bent at the knee to
being locked vertically straight. The range of the gait when the foot is off the ground.
Switch Control: Use of electric switches to control current from a battery to operate an electric
elbow, wrist rotator, or terminal device
Symes Amputation: An amputation through the ankle joint that retains the fatty heel pad portion
and is intended to provide end bearing weight.
Temporary Prosthesis: A prosthesis made soon after an amputation as an inexpensive way to
help retrain a person to walk and balance while shrinking the residual limb.
TEC: Total Environmental Control liner.
Terminal Device: Device attached to the wrist unit of an upper extremity prosthesis that pro-
vides some aspect of the function (grasp, release, cosmesis, etc.).
TES Belt: A neoprene or lycra suspension system for AK prostheses that has a ring that the pros-
thesis slides into. There is a neoprene belt that attaches around your waist by Velcro or a hook
and loop fastener. It is used to give added suspension of a prosthesis and/or control rotation.
Test Socket: A temporary socket, often transparent, made over the plaster model to aid in ob-
taining proper fit.
Therapeutic Custom Shoe: A shoe designed and fabricated to address an individual's medical
condition. A therapeutic custom shoe is made over a modified positive model of an individual's
foot and can be either custom-molded or custom-made.
Toe-off: Transferring weight from the toe to begin the swing phase. “Toe off” refers to the in-
stant of final contact between the shoe and the floor; generally the very front, bottom edge of the
Torque-Absorption Unit: This device allows amputees to turn their body while keeping the
prosthetic foot in the correct position giving them a more natural swing due to the amount of ro-
tation provided by the unit.
Total Contact: Total contact between the limb and socket at all points.
Transfemoral Amputation: For an above-the-knee (AK) amputee part of the femur remains in-
tact as part of the residual limb. The transfemoral amputee has to consider the type of knee unit,
the choice of foot and how well the combination will perform as a unit. For many transfemoral
amputees, walking on rough ground can increase the risk of stumbling so it is important to
choose a knee unit that will allow some degree of recovery from such a stumble. The amputee
can vary the amount of knee resistance with a simple adjustment of the knee unit.
Transtarsal Amputation: Through the tarsal (tarsus) or foot bones.
Transtibial Amputation: For a below-the-knee (BK) amputee, part of the tibia remains intact as
part of the residual limb. For the transtibial amputee, the focus is on the type of prosthetic foot
used. For walking on uneven ground, the amputee should choose a foot that offers multi-axial

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motion combined with energy return or dynamic response. This ensures that the foot maximizes
contact with the ground at all times and offers a high degree of energy return to the user.
Traumatic Amputation: An amputation that is the result of an injury.
UE - Upper Extremity: Having to do with the upper part of the body in reference to amputees,
arms or shoulder amputations.
Verrucous Hyperplasia: A red, raised, circular area on the distal end of a residual limb caused
by an air pocket and suction being applied to the end of the limb from the liner. This condition
frequently occurs when the residual limb does not make total contact with the bottom of the
Voluntary-Closing Devices: Terminal devices that are closed by forces on a control cable; grasp
is proportional to the amount of pull on the cable.
Voluntary-Opening Devices: Terminal devices that are opened by body motion and closed by
elastic bands or springs.
WD - Wrist Disarticulation: Amputation through the wrist.

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                               APPENDIX C
                        ACRONYMS AND ABBREVIATIONS
AAOP            American Academy of Orthotists and Prosthetists
ABC             American Board of Certification
ACA             Amputee Coalition of America
AE              Above the Elbow (“transhumoral.”)
AOPA            American Orthotic and Prosthetic Association
APL             Applied Physics Laboratory
BK              below the knee
BOC             Board for Orthotists/Prosthetists Certification
CAD             computer-aided design
CAM             computer-aided manufacturing
CP              certified Prosthetist
CPO             certified Prosthetist Orthotist
CSOP            Clinical Standards of Practice
DARPA           Defense Advanced Research Projects Agency
DAK             Double Above Knee
DDM             direct digital manufacturing
DLA             Defense Logistics Agency
DMC             Defense Manufacturing Conference
DoD             Department of Defense
ED              elbow disarticulation
FDA             U.S. Food and Drug Administration
FY              fiscal year
HO              heterotopic ossification
HD              hip disarticulation
HP              hemipelvectomy
IAOP            International Association of Orthotics and Prosthetics
IED             improvised explosive device
IPOP            Immediate Post Operative Prosthesis
ISO             International Standards Organization
KD              knee disarticulation
LE              lower extremity
MCM             motor control mechanism
mo              month

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MRL             manufacturing readiness levels
NASA            National Aeronautics and Space Administration
NGMTI           Next Generation Manufacturing Technology Administration
O&P             orthotics and prosthetics
ORNL            Oak Ridge National Laboratory
OSD             Office of the Secretary of Defense
R&D             research and development
RPP             Revolutionizing Prosthetics Project
SACH            solid ankle cushioned heel
SBIR            Small Business Innovative Research
TRL             technology readiness levels
TDK             through the knee
TEC             total environmental control
TES             total elastic suspension
TPE             thermoplastic polyester elastomer
UE              upper extremity
UK              United Kingdom
USOC            United States Olympic Committee
UV              ultraviolet
VA              Veterans Administration
WBS             work breakdown structure
WD              wrist disarticulation

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