Lower limb amputation Part Prosthetics year literature review

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					             Prosthetics and Orthotics

 Lower limb amputation Part 3: Prosthetics - a 10 year literature review
                           H. Cochrane, K. Orsi and P. Reilly
                            Prosthet Orthot Int 2001 25: 21
                           DOI: 10.1080/03093640108726564

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Prosthetics and Orthotics International, 2001, 25, 21-28

                          Lower limb amputation
              Part 3: Prosthetics - a 10 year literature review
                             H. COCHRANE, K. ORSI and P. REILLY

          Prosthetics and Orthotics Education Programme, George Brown College, Toronto, Canada

Abstract                                                           Purpose
   This paper is intended as a follow-up to the                       The objective of this study was to investigate
ISPO Consensus Conference on Amputation                            literature published after 1990 that pertained to
Surgery. It reviews all the literature on lower                    lower limb prosthetics and identify the major
limb prosthetics published after 1990. The                         advances and innovations which occurred over
review was considered under six categories:                        the last decade. This literature review is to be a
feet,      knees,     hips,      thermoplastics,                   continuation of the 1990 ISPO Consensus
liners/suspension and computers.                                   Conference, which produced the ISPO
                                                                   publication "A Consensus Conference on
Introduction                                                       Amputation Surgery". This publication studied
   Prosthetic devices have been used for                           earlier prosthetic developments with respect to
centuries to aid amputees in maintaining their                     rehabilitation and prosthetic procedures.
quality of life and assist in their activities of                  Identification of advances and innovations
daily living. The earliest written report of the                   should bring to light current trends in lower limb
use of a prosthesis is in the Rig-Veda                             prosthetics and aid in education.
period between 3500-1800BC (Lim, 1997).
Since that time the field of prosthetics has                      Methods
continued to evolve. In the last decades rapid                      An extensive search of the RECAL database
advancements, not seen in other historical                        at the University of Strathclyde, in Glasgow,
periods, have occurred. In each decade                            Scotland was performed. The database search
prosthetic professionals have displayed a unique                  included articles from the past decade, (1990
ability to look to other fields and see how growth                and later) covering the following topics:
in these fields may be applied to prosthetics.                    Prosthetic* and Feet*
This has allowed for the creation of prosthetic                   Prosthetic* and Knee*
devices, which continue to meet or exceed the                     Prosthetic* and Hip*
expectations of prosthetic users. The focus of                    Prosthetic* and Suspension*
this literature review is to identify the major                   Prosthetic* and Liner*
advances and innovations of the 1990s, which                      Prosthetic* and Socket* and Design*
has seen prosthetic professionals build on                        Prosthetic* and Computer*
proven principles, quantify their achievements                    Prosthetic* and Material*
and improve upon earlier advances.                                  (Note: * indicates a wild card, which searches
                                                                  the different tenses of each word and plurals)
                                                                    The search yielded in excess of 4,000 articles,
                                                                  and as a result constraints were applied. Articles
All correspondence to be addressed to P. Reilly,
                                                                  were restricted to publication in the English
GBC Prosthetic and Orthotic Education Programs,
c/o SCIL, Sunnybrook and Women's College Health                   language, with the exclusion of case studies,
Science Centre, 2075 Bayview Avenue, Toronto, ON,                 anecdotal literature, articles dealing solely with
Canada M4N 3M5. Tel: (+1) 416 480 5783;                           pathologies; pediatrics and sport-related devices.
Fax: (+1) 416 480 5975; E-mail:                      To accomplish an unbiased and informative
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22                                   H. Cochrane, K. Orsi and P. Reilly

study the opinions of a diverse group of                          in a variety of areas. Examples of these
international prosthetists were recruited. Each                   improvements include the ability to control the
prosthetist who agreed to participate received a                  dynamic load and the memory return of the
scope of study document, defining the objectives                  material once that load is removed. These new
of the study and the parameters. These                            materials have allowed for prosthetic feet to
individuals were sent an article list, including                  become increasingly lighter and more cosmetic
relevant bibliographic information and abstracts.                 (Lim, 1997). In the 1980s a new generation of
Additionally, a questionnaire was included with                   feet were developed, Stationary Ankle Flexible
the article list, requesting the prosthetist to                   Endoskeletal (SAFE) foot and dynamic elastic
indicate the articles they felt best reflected the                response or energy storing feet, in an attempt "to
advances that occurred in the period between                      develop more true to life and energy efficient
1990 and 2000. The prosthetists were asked to                     modular components" (Lim, 1997). These
comment on or express any concerns with regard                    designs were highly successful and allowed
to specific articles and on the study in general,                 prosthetic users increased freedom with respect
either in format or content. Once responses were                  to the activities one could participate in. The
returned, they were combined on a master list                     1990s witnessed a continued evolution in these
and commonly indicated articles were collected                    designs as increased demands have been placed
and studied. In select instances articles not                     upon them. The introduction of new prosthetic
indicated by the majority were included within                    feet has tended to raise the functional standards
the study. This occurred if the recommending                      but at the same time has caused difficulty in
prosthetist provided comments about relevance                     identifying the most significant advances.
of the particular article.                                        Prosthetic feet should be looked at as a continual
   It was noted by one of the participating                       evolution, often reflecting the trends and
prosthetists that the study had the propensity to                 demands of the users.
be biased towards technological advances and as
a result neglected advances that occur in low                     Knees
income countries. In these countries, the                           Modern prosthetic knees have seen a trend
population of amputees is much greater with a                     toward the development of knee mechanisms
tendency that this growth will continue. This                     that better simulate normal knee function both in
may lead one to believe the advances made in                      stance and swing phases. Until recently
prosthetics in these settings would make a                        mechanical knees used in prosthetics have
significant impact on the field and in turn would                 weaknesses in two areas: failing to permit
not necessarily be included within this study.                    controlled knee flexion in weight bearing and
This bias is attributed to the fact that the                      gradual extension of the knee under load. When
participating prosthetists and much of the                        these weaknesses are eliminated within the
literature was from industrialised nations.                       prosthetic knee, the amputee is no longer
   The results of the questionnaire and literature                required to walk with a fully extended knee
search were sub-divided into six categories, feet,                during stance phase, thus allowing several
knees, hips, thermoplastics, liners/suspension                    biomechanical advantages to occur:
and computers for the purpose of organisation.                    • a combination of plantarflexion of the ankle
                                                                    and knee flexion decreases the time spent
Feet                                                                between heel strike and foot flat, bringing the
  In order for any lower limb prosthesis to                         amputee to a more stable position earlier;
function optimally the appropriate prosthetic                     • stance flexion provides a cushioned support
foot needs to be implemented. One author noted                      with gradual weight transfer onto the forward
that "the ideal prosthetic foot would imitate                       leg;
perfectly the human foot in form and function.                    • limiting the raise of the centre of gravity
This is not possible given the current                              allows for a smoother forward progression of
technology" (Romo, 1999). This is true despite                      the body than is possible with a stiff knee
the fact that the selection of prosthetic feet has                  mechanism. This results in an improvement in
been seen to grow unceasingly. Prosthetic feet                      the amputees' overall gait;
have seen the incorporation of new designs and                      (Blumentritt et al, 1997; Michael, 1999).
materials, to improve the dynamic performance                       Each of the advantages create a more efficient
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                                     Lower limb amputation: prosthetics                                           23

gait by limiting the oscillation of the centre of                 walking (Michael, 1999). Both the Endolite
 mass, reducing energy expenditure.                               Intelligent Plus and the Seattle Limb Systems
   Knee mechanisms allowing stance phase                          Power knee offer similar microprocessor
flexion have been developed over the last                          systems (single on-board sensor) within the knee
decade. The early part of the decade saw the                      that detect full knee extension and adjust a
development of a method using a polycentric                       pneumatic swing control mechanism to match
knee with a polymeric spring. The spring                          the individual's gait. The microprocessor allows
cushions the increased load with weight transfer                  the amputee to have a range of gait velocities
and allows up to 15 degrees of stance flexion                     from very slow to very fast. Two benefits seen
(Blumentritt et al, 1997).                                        with these microprocessor knees is the improved
   More recently, the 1990s saw the development                   gait symmetry and responsiveness in swing
of a rotary hydraulic knee, offering a load                       phase as well as the amputees' perception that
dependent hydraulic stance stability and a                        the prosthesis is responding more consistently,
hydraulic swing phase mechanism (Otto Bock                        leading to a greater confidence in the prosthesis
3R80). The significance of the knee is seen when                  (Michael, 1999). Studies investigating the
one examines the method used to obtain stance                     effects of the microprocessor knees on energy
phase flexion resistance in earlier hydraulic                     expenditure demonstrated that there was a 10%
mechanisms. In the past, initiating stance phase                  decrease from a conventional prosthesis at
flexion, required two conditions; 1) the knee                     velocities greater than 3.2 km/hr (Taylor et al,
must be in full extension, (causing the piston to                  1996; Buckley et al, 1997). Decreased energy
be at the limit of its travel) and 2) knee                        expenditure can be observed as a result of the
hyperextension moment must be applied for at                      inherent ability of the knee microprocessor to
least 0.1 of a second. Typically these conditions                 accommodate for variable gait velocities.
are met at terminal stance, however they can be                   Amputees also stated that the microprocessor
met inadvertently during a loading response                       knee was not as tiring as the conventionally
(Blumentritt, et al, 1998). The rotary knee                       dampened knee and that manoeuvring around
mechanism is able to offer automatic stance                       obstacles was easier (Taylor et al, 1996). A
control throughout weight acceptance. In                          further progress in the microprocessor knees was
addition it automatically disengages during pre-                  the development of the C-leg by Otto Bock.
swing with the gradual shifting of load to the                    Rather than a pneumatic swing control
contralateral limb. The hydraulic stance stability                mechanism a hydraulic unit is used, allowing for
is triggered consistently and predictably in                      a greater range in gait velocity. The C-leg also
weight bearing when a load is applied to the                      incorporates a variable hydraulic stance phase
prosthesis and cannot be inadvertently                            control, which uses multiple sensors to collect
disengaged during stance by loading the forefoot                  and calculate biomechanical data to adjust the
or by generating a hyperextension moment.                         knee according to the amputees' desired gait
There is also a secondary trigger axis anterior to                velocity. This data is collected 50 times per
the rotary axis that in combination with a                        second.
compressible elastic bumper allows the knee to
have 4 degrees of stance flexion, without                         Hip
affecting stability (Blumentritt, et al, 1998).
                                                                    At more proximal levels of amputation the
  Another advance in prosthetic knees is the use                  challenges of prosthetic fitting are magnified
of computer technology that has been applied for                  and complicated further by bilateral
a number of years to upper limb prosthetics and                   amputations. In the case of bilateral hip
is now finding applications in lower limb                         disarticulations and hemicorporectomy, the
prosthetics. Amputation levels, which require                     skeletal structure and soft tissue available for
prosthetic knee joints, have seen the                             weight bearing are significantly compromised
incorporation of microprocessors to improve                       and result in an increased incidence of skin
individual gait patterns with respect to cosmesis                 breakdown. When one considers the
and stability, while allowing for a wide range of                 physiological loss in this type of amputation it is
walking velocities. It is no longer necessary for                 important to realise that not only have weight
the prosthetist to find the best compromise of                    bearing surfaces been lost but also skin surface
knee resistances between very fast and very slow                  area, vital to heat dissipation. In combination

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24                                    H. Cochrane, K. Orsi and P. Reilly

with the loss of skin surface area, heat                             suitable material for projects in the countries
dissipation is further complicated by the                            where the ICRC operates. It is cheap,
traditional socket designs consisting of                             recyclable, light and easy to transport and
thermoplastic or thermosetting materials which                        store."
are not permeable to air and envelop much of the                     In addition it was noted by Schuch (1990) that
remaining tissue of the torso. One research                        the fabrication time and procedure for
group noted this and in an effort to improve                       thermoplastic sockets was quick and simple
upon existing sockets a flexible air-permeable                     when compared with traditional lamination
socket was designed (Carlson and Wood, 1998).                      techniques. This process leaves greater room for
Rather than seeking out new materials and                          human error and is often more time consuming
procedures, this group applied proven materials                    than a thermoplastic moulding. It should be
(cotton) and techniques (sewing) to develop a                      noted that a safer work environment could be
new socket type. This new socket consisted of a                    established with the use of thermoplastics as
corset custom fitted to the client, which included                 they yield less harmful vapours and dust as
a custom-made bottom and was supported by a                        compared to laminates. Thermoplastics are often
custom frame which was fenestrated to allow air                    thought to be less durable for long-term
and heat to pass through. This design also                         prosthetic use than laminates. However both
allowed for independent motion of the corset                       Schuch, (1990) and Verhoeff et al. (1999),
within the frame and accommodated for volume                       found that the long-term use of thermoplastic
fluctuation and associated contour change. The                     sockets came with no additional risk of wear and
value in this innovation is not just the socket                    tear of the socket material than if traditional
type but the reminder that sometimes everything                    laminates had been used.
old can be new again. The authors wrote that                          "Excepting very early attempts with extremely
"We should all be aware that when we confine                         thin Surlyn flexible sockets, this author has
our creative thinking to what we can design with                      found thermoplastics to be significantly more
new materials and new fabrication processes, we                       durable than thermoset laminated sockets"
overlook some very rich resources" (Carlson and                       (Schuch, 1990).
Wood, 1998).                                                         The researchers for the ICRC (Verhoeff et al,
                                                                   1999) concluded that in a study of forty-three
Thermoplastics                                                     prostheses over an average three year period of
  Although thermoplastics were utilised well                       use only two devices had plastic weld failures
before 1990, the prevalence of their use has                       which were attributed to human error. It is also a
increased over the last decade as a result of                      significant note to recognise that both devices
many factors. The advantage of thermoplastics                      were still being worn sixteen hours per day.
coincide with social and economic changes that                        These factors combine to indicate that
have occurred over the past ten years, making it                   thermoplastics are a viable option for the use of
a more appealing prosthetic option than ever                       as a material for prosthetic sockets as they are
before. The social trend towards protection of                     also both economical and safe.
the environment and natural resources makes the
recyclable properties of plastics like                             Liners and suspension
polypropylene an appealing option as it reduces                      Despite the fact that the use of prosthetic
the volume of waste produced in the fabrication                    interface liners is not new, the past decade has
process. This recyclable quality further appeals                   seen continued development through various
where raw materials are limited (e.g. developing                   materials and designs. This progression attempts
countries) as it allows for all available materials                to create a more comfortable and cosmetic
to be used without wasting cut-off or remnants.                    socket, while reducing the incidence of skin
Writers for the International Committee of the                     breakdown. Development of socket liners began
Red Cross/Crescent (Verhoeff et al, 1999)                          in the 1980s and continued on into the 1990s.
noted that about 50% of the prosthetic devices                     The creation of internal suspension mechanisms
they introduced in the early 1990s were                            or suction sockets allowed for the elimination of
produced of polypropylene These authors stated                     external strapping systems. These external
that                                                               systems are often bulky, cumbersome and
  "Polypropylene has proved to be a very                           generally felt to be less cosmetic. Further
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                                      Lower limb amputation: prosthetics                                           25
advantages gained by the internal suspension                       materials and cloth liners to improve the
mechanisms are the reduction in the amount of                      resilience. In addition the dampening properties
piston action between the prosthesis and the                       and reduction of shear forces are continually
stump, and the increase in the freedom of                          improving, however certain problems still exist.
movement (Dietzen et al, 1991). Despite the                        Therefore further research and development is
ingenuity of the design some inherent                              required before all those who could benefit from
weaknesses are:                                                    these liners, find themselves to be appropriate
• limited space which does not permit the                          candidates.
   installation of the attachment mechanisms;                         Incidence of dermatological problems also
• difficulties in donning the prosthesis due to                    effect prescription of liners. In the investigation
   deficiencies in upper limb either in strength or                by Lake and Supan (1997), dermatological
   dexterity, and where impaired vision is                         problems were attributed to socket fit, hygiene,
   present;                                                        patient pathologies, and/or heat and were seen to
• additional weight of the prosthesis, as well as                  be influenced primarily by age, level of activity,
   cost and time required for fabrication                          and how long the individual has been using a
• disproportionate distal stump shrinkage due to                   liner. Within the literature reviewed by Lake and
   milking action created by the prosthesis on the                 Supan (1997), they acknowledge the following
   stump;                                                          problems that have been seen to occur with use
• increased complexity;                                            of silicone liners:
   (Haberman et al, 1992).                                         • a period of excessive perspiration, irritation as
   The 1990s saw research into new materials                          initial side effect and then after a period of
used in prosthetic liners, taking advantage of                        time, seen to subside. (Antiperspirants were
their impact dampening properties to reduce skin                      also noted to be effective in decreasing the
breakdown and create a more comfortable                               amount of perspiration);
socket. This is in order to improve upon the                       • in warm environments and summer months,
shortcomings of preceding liners. As stated by                        an increase in warmth and moisture within the
Emrich and Slater (1998), the goal is to create a                     socket occurs, promoting skin maceration, and
total contact fit, diffusing pressure over the                        favoring a situation that encourages bacterial
entire stump and to avoid excess stump                                invasion in to the hair follicles;
movement. Emrich and Slater (1998) felt that to                    • an increase in heat rash created as a result of
accomplish this goal the coefficient of friction                      the interference between the liner the body's
between the stump - liner and the liner - socket                      natural heat dissipation mechanisms
must be high, minimising the movement                                 (radiation, convection, conduction and
between these two interfaces. In addition the                         evaporation);
force transmitted from the liner to the stump                      • physiological changes in the skin, due to
must be low enough that no ill effects occur.                         aging, lowers the skins threshold to shear
Once the requirement of a high coefficient of                         forces and decreases the contact area (areas
friction is met, it was noted that the materials                      most noted for shear abrasions are the
should allow for variability in fit, to                               proximal liner trimline and posterior distal
accommodate fluctuations in volume, while still                       aspect of the stump);
maintaining proper contact and alignment on the                    • combination of naturally oily skin and
stump. Since the prosthetic liner is under                            increase in pressure created by socket leads to
constant load either via tensile stress (from the                     an incidence of folliculitis;
liner being pulled upwards by the stump and                        • pain, elicited by the pulling action of the liner
simultaneously downwards by the prosthesis),                          on the stump and irritation at the posterior
compressive stress when standing and in the                           aspect of the knee from bunching/wrinkling of
donning procedure, durability of the liner is a                       liner/socks with knee flexion;
major consideration in its prescription. Results                   • possible allergic reactions to silicone causing
indicate that silicone and polyurethane liners                        dermatitis. However, silicone is considered
although lacking in durability also reduce the                        the safest biomaterial available and
amount of shear forces that may be responsible                        hypoallergenic, therefore reactions maybe the
for skin breakdown. Subsequent designs have                           result of rubber accelerators or antioxidants,
addressed durability issues by adding matrix                          not normally present in silicone.
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26                                    H. Cochrane, K. Orsi and P. Reilly

   Other contributing factors to dermatological                    (computer aided design/computer aided
problems were found to be; cause of amputation,                    manufacture), which during the 1980s saw the
age, whether powders, deodorants or sheaths                        fruition of ideas and theories conceived as early
were used, activity level and previous methods                     as the 1960s (Houston et. al, 1992). But, as
of suspension (Lake and Supan, 1997).                              much of the early literature shows, the systems
Amputees at risk for dermatological problems                       were complex and
associated with liners were found to be those                         "Criticised as being capable of fast production
with high activity levels (i.e. high perspiration),                   of mediocre - fitting prosthetic sockets"
traumatic amputees and those with pre-existing                        (Hastings et al, 1998).
dermatological problems.                                              By the early 1990s, it was recognised that in
   While some literature advocates the use of                      order to use this technology to improve the
powders and deodorants with the liner,                             quality and efficiency of the prosthesis being
dermatological problems are seen to be higher                      provided, the technology must continue to
when they are utilised. Often these substances                     transform into a system that was more user
leave a residue against the skin leading to                        friendly and consistent. Since the technology of
irritation. Use of sheaths on the other hand,                      the 1980s was no more cost effective or less time
showed a decrease in the level of skin problems.                   consuming than traditional methods of socket
Three features of the sheath are cited as to why                   fabrication, the fiscal incentive to use and
this occurs: they act as a wick to remove                          develop CAD/CAM did not materialise. In 1992,
moisture, they allow a small amount of air to                      a comprehensive study by the Department of
circulate around the stump, and facilitate the                     Rehabilitation Medicine at the New York
removal of direct contact of the liner with the                    University Medical Center for the Department of
skin. This also reduces shear forces on the skin                   Veteran Affairs was published. It was designed
at the proximal trimline of the liner (Lake and                    to address key issues identified by prosthetic
Supan, 1997).                                                      researchers, practitioners, and rehabilitation
   Research into the materials of socket liners                    health care experts (Houston et al, 1992). The
have revealed advantages and disadvantages of                      objectives of this study were to introduce
various types of liners. Consideration should be                   CAD/CAM technology, evaluate its feasibility,
given to each of these when assessing the                          developmentally test, evaluate and obtain
individual amputee and their requirements.                         quantitative data in order to refine the system.
                                                                   These researchers found that it took up to 4 days
Computers                                                          to learn how to use the system (even with little
  Like many other industries computers have                        or no experience with computers) and noted that
increasingly become a part of the business of                      to obtain a reasonable proficiency it was
prosthetics in the last decade. Not only have they                 necessary to fit at least 4 amputees with varying
found a place in the business aspects by helping                   characteristics (e.g. size, shape etc). In addition,
maintain accurate records and billing                              it was noted that the average turn around time
procedures, they have also helped in the                           for design and fabrication was 2.6 days. This
exchange of information between professionals                      would clearly indicate an acceptable learning
and prosthetic users. As the internet has                          curve and fabrication time and allow for the
developed as a means of information exchange                       greatest achievements in efficiency. Within the
and advertising, solutions or suggestions to even                  duration of the study several upgrades were
the most rare and complex prosthetic problems                      performed on both the hardware and software.
can be obtained through a variety of sources and                   Researchers noted that the repeatability and
received or sent from almost any part of the                       accuracy were low, which was attributed to the
world. Although this technology was present                        digitiser and technique used for data collection.
long before the scope of this study, it must be                    Incorporating a new electromechanical digitiser
noted because of its enormous proliferation and                    and transducer for positional measurements
impact in the last ten years.                                      rectified this inconsistency. Early data showed
                                                                   that communication errors between the
  On the other hand, the most interesting
                                                                   computer and the carver resulted in system
application of prosthetics and computers is their
                                                                   errors, resulting in a loss of patient data 30% of
use in socket design and manufacturing. This
                                                                   the time. To eliminate this loss of data, software
development is better known as CAD/CAM
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                                     Lower limb amputation: prosthetics                                                     27

was added to improve the communication                            to Heather Smart and the RECAL staff, Dan
acknowledgement between the two systems and                       Blocka, and all prosthetists who participated in
resulted in a reduced incidence of                                this study.
miscommunication to a 5% ratio of error.
Further enhancement to the software that
occurred during the study, included
improvements to the contour, smoothing and                                                    REFERENCES
correction of errors in the back-up system. The
researchers found that a host of problems                            The list below include all articles indicated as
occurred in the fabrication process, not the least                significant by the participating prosthetists.
of which was the wear and tear on the parts of                    Although some may not be cited within the
the forming machinery, as a result of                             literature all were read for their significance and
asymmetrical casts. Improvements were made to                     used to identify the past decade's innovations
the durability, in addition to the information                    and advancements.
relay software, so that those improvements
could be made. These researchers concluded that                   AEYELS B, PEERAER K, VAN DER SLOTEN J (1992). Van
the future research could be concentrated on                          der Perre G. Development of an above-knee prosthesis
more expedient and comprehensive ways of                              equipped with a microcomputer-controlled knee joint:
                                                                      first test results. J Biomed Eng 14, 199-202.
characterising the information gathered from the
stump and inputting it into the CAD/CAM                           BLUMENTRITT S, SCHERER HW, MICHAEL JW, SCHWMATZ,
systems. It was felt that the design capabilities                     T (1998). Trans-femoral amputees walking on a rotary
                                                                      hydraulic prosthetic knee mechanism: a preliminary
should be expanded to all levels of amputation,                       report. J Prosthet Orthot 10, 61-70.
allowing for a greater functional use of the
system. These features are improved with each                     BLUMENTRITT          S,     SCHERER   HW,   WELLERSHAUS   U,
generation of CAD/CAM systems.                                        MICHEAL JW (1997). Design principles, biomechanical
                                                                      data and clinical experience with a polycentric knee
  In addition to these advances there is also the                     offering controlled stance phase knee flexion: a
innovation of microprocessors into knee units                         preliminary report. J Prosthet Orthot 9, 18-24.
such as the C-leg, which incorporate computers                    BUCKLEY JG, SPENCE WD, SOLOMONIDIS SE (1997).
into their alignment and assessment process.                          Energy cost of walking: comparison of "Intelligent
                                                                      Prosthesis" with conventional mechanism. Arch Phys
                                                                      Med Rehabil 78, 330-333.
   The last decade has seen a host of changes that                CARLSON JM, WOOD SL (1998). A flexible, air-permeable
effect all aspects of prosthetics. They often come                  socket prosthesis for bilateral hip disarticulation and
as part of the natural evolution of prior advances,                 hemicorporectomy amputees. J Prosthet Orthot 10,
that are continually challenged by an ever
demanding user population and increasingly                        CHAKRABORTY JK, PATIL KM (1994). A new modular six-
skilled and educated prosthetic professionals.                        bar linkage trans-femoral prosthesis forwalking and
                                                                      squatting. Prosthet Orthot Int 18, 98-108.
   Although great strides have been made with
respect to componentry it is difficult to decipher                DIETZEN CJ, HARSHBERGER J, PIDIKITI RD (1991). Suction
whether these can be considered significant. As                       sock suspension for above-knee prostheses. J Prosthet
                                                                      Orthot 3, 90-93.
a result, one component would have difficulty
representing the greatest innovation over the last                EMRICH R, SLATER K (1998). Comparative analysis of
decade.                                                             below-knee prosthetic socket liner materials. J Med
  The ability to quantify and validate a                            Eng Technol, 22, 94-98.
particular device, procedure or practice can be                   ENGSBERG JR, CLYNCH GS, LEE AG, ALLAN JS, HARDER
considered an advancement and is seen to                              JA (1992). A CAD/CAM method for custom below-
facilitate future research. The past decade                           knee sockets. Prosthet Orthot Int 16, 183- 188.
continues the evolutionary process of all aspects                 FREEMAN D, WONTORCIK L (1998). Stereolithography and
of prosthetics, allowing the amputee the                              prosthetic test socket manufacture: a cost/benefit
possibility of fulfilling their desired lifestyle.                    analysis. J Prosthet Orthot 10, 17-20.

                                                                  HABERMAN LJ, BEDOTTO RA, COLODNEY EJ (1992).
Acknowledgements                                                      Silicone-only suspension (SOS) for the above-knee
 The authors would like to express their thanks                       amputee. J Prosthet Orthot 4, 76-85.
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28                                       H. Cochrane, K. Orsi and P. Reilly

  DRVARIC DM (1998). Frequency content of prosthetic                      HFJM, EISMA WH (1997). Energy storage and release
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  digitizer performance. J Prosthet Orthot 10, 2-6.                       storing and 2 conventional feet, user choice of foot and
                                                                          deciding factor. Prosthet Orthot Int 21, 28-34.
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