VIEWS: 5 PAGES: 21 POSTED ON: 2/13/2011
1-Prosthesis Definition: A device used to replace an absent body part whether due to trauma, disease or congenitally absent ones. Prosthesis of the upper limb may be cosmetic, functional or combination of both. - Arm function to place hand in adequate position to fulfill a particular task. - Hand tasks: 1- Manipulative tasks. 2- express feeling. 3- Explore environment. - No prothesis can replace all function satisfactory. Selection is based in specific requirement of the amputee. Types of prosthesis & control systems: 1- Cosmetic: This is the simplest and lightest type available. For transradial (forearm = below elbow) it consists of 1- Foam filled glove with 2- Wired fingers 3- Fitted to a self- suspending socket. 2) No control system required For higher levels: 1) There is a need for a prosthetic elbow joint. 2) An endoskeletal system is used that consists of: a) Same hand as above (attached to) b) Foam covered tube forearm. c) Upper arm section attached to the socket. d) socket may be: 1- Simple figure of eight appendage for suspension. 2- Self suspending socket. Advantage of this prosthesis It provides best cosmetic replacement but with minimal functional benefit e.g.: Holding objects steady or carrying things over forearm. N.B: Individually sculpted silicon hands are available which are excellent cosmetically but expensive and not strong enough for any practical daily tasks. II) Functional U.L. Prostheses: A) Body powered: This prosthesis is the simplest functional prostheses. Body movement is harnessed to control the terminal device (and elbow). A set of appendages harness the body movement: Example (1) biscapular protraction, (2) shoulder flexion (and elbow extension = in cases of transradial amputation) are used to control terminal device. (2) Shoulder depression, extension, internal rotation, & abduction operate the elbow lock in trans humeral amputation. This type of prosthesis is a working tool & it is functional rather than attempting to be cosmetic (B) Electric Powered: Idea: A battery – operated motor moves the hand and/or gripper, wrist or elbow by either. 1- Myo-electric control. 2- Servo control. 3- Switch control. Rechargeable batteries are mounted within the prosthesis and delivered with charger. 1- Myo-electric control: Electrodes pick up microvolts of electricity produced by contractions in the muscles of the residual limb. Signals are amplified and thereafter they activate the motor. In operating hand there may be 2 electrodes; one on extensor muscles and one of flexor muscles groups for opening & closing the hand respectively. Alternatively a single site placement for voluntary opening & automatic closing can be used. Wrist movement can be controlled myo-electrically using 2 site system. An electric elbow lock can be activated be a single site placement. 2) Servo Mechanisms: The same movements used to control body powered prosthesis, can operate an electric hand but with less shoulder girdle movement. Where mechanical energy is transmitted into electric energy to operate the device motor(s). 3) Switch control: Using harness or touch pads to control electric devices in different ways. N.B.: Electrically powered prosthesis are not recommended for primary amputee's because they are: (a) Heavy (b) require close fitting socket. (c) More complex to operate & care for. They can be considered 6 months post amputation when edema has completely resolved, and the amputee has enough experience with either body powered or cosmetic prosthesis. Terminal devices - Used to replace the task of the hand, - It may be cosmetic or functional / passive or active. The most commonly used active functional device is the split hook: It consists of once static – one movable new. Grip in achieved by elasticated bands holding the two jaws together, and can be increased by increasing number of bands. The device is activated by harness attached to the lever of the moving jaw as residual limb moves, harness pulls the jaw open, providing good proprioceptive feed back. If cosmoses are important, a cosmetic hand can be provided: (Cosmetic hand see above). If patient seeks combination between cosmoses and function, same device as above is used but with mechanical hand same shape as the human hand and body power pulling the thumb and fingers apart. But it has some disadvantages, as it is harder to operate than the split hook, has poorer grip, bulky & making precision difficult. However it is helpful if an amputee not demands high level of manipulative skill from the prosthesis. Terminal devices with special tasks: - Active: pliers – tweezers (using operating cord). - Passive: hammer, fishing red holder tool holder. 2-Prosthetic joints: Wrist unit: A cylindrical wrist unit either hand or electrically operated to provide 360° rotation, allow positioning of the terminal device in adequate supination/ pronation range for the required task. Usually wrist units have a disconnect facility allow change of terminal device. Elbow joint: Several forms of prosthetic elbow joints are in use. Hand operated joints are commonly used with cosmetic prosthesis. In addition, body powered elbow joints, used with body powered prostheses, are utilized. They are operated using operating and elbow lock cords. Operating cord operates the terminal device when the elbow is locked, while with elbow unlocked it operates the elbow joint. Suspension: For hand amputation and wrist disarticulation self suspension is used that depends on hanging the socket to bony prominences, namely radial and ulnar styloid processes. For transradial amputation when using a supra condylar socket, self suspension is applied using medial and lateral humeral epicondyles for hanging the prosthesis. When cup socket is utilized a simple figure of eight appendage suspension id applied. For transhumeral amputation appendage suspension is utilized. N.B.: In case of transradial amputation cup socket is used when amputee need carry heavy objects, with very short residual limb, or bilateral amputation. Supracondylar socket is used with cosmetic and passive terminal devices. In wrist disarticulation supination /pronation is controlled by wrist unit or by split socket with one section at the wrist and the other at the distal part of the arm, sparing the forearm to perform movement. Lower Limb Prosthesis Types of lower limbs prostheses : Types of L.L. prostheses depend on different stages after amputation. There are three types: Immediate post- operative prosthesis, temporary prosthesis, and definitive prosthesis. I- Immediate post- operative prosthesis - Used for young patients, usually after a traumatic injury. - Consists of rigid dressing (formed of plaster or fiber glass padded with felt, cotton, or poly urethane), pylon, and foot. - Pylon is usually made of aluminum, steel or plastic. - It helps patient to gain psychological support, early walking (with assitive device 5-12 days post operative) leads to less hospital stay, and reduce phantom pain. Disadvantages are the possibility of impaired healing & falls due to early ambulation. Contraindication: 1- History of slow wounds healing. 2- Extreme obesity. 3- Excessive preoperative edema. 4- Lack of 45 days preoperative ambulation. II – Temporary prostheses: It is usually used for 3 to 6 month after amputation. It helps early weight bearing, and reduces edema in the residual limb stamp. The most common type of temporary prosthesis is adjustable prosthesis. It consists of a socket, pylon, foot. It can be modified so that the foot in moved in medial, lateral, anterior, posterior inversion, eversion direction. These adjustments help to correct gait deviations, increase energy efficiency, and make walking more efficient and cosmetic. Therefore it is used in early stages of gait training. Temporary prosthesis can be converted to definitive or final prosthesis with cosmetic modifications. IV- Definitive prosthesis It is used when limb volume becomes stable. It can be applied 3-9 months postoperative. Life span 3-5 years. Changes are needed when there is 1- Residual limb atrophy. 2- Weight gain or loss. 3- Excessive wear after prosthesis. Designs of L.L. Prostheses Endoskeletal (Modular) Ex oskeletal IPOP, temporary, or definitive Defenitive only used in occupations that need high durability or dealing with heat. Components 1- Socket Hard outer cover made of plastic 2- Pylon made of steel, laminate. aluminum, titanium or Socket is sculpted or built in. carbon (carbon is used with flex foot). 3- Prosthetic foot. 4- Shock absorbing unit bumpers, or springs or fluid full) attached socket (above) or foot (below) 5- Finishing : soft foam, or prosthetic skin 3-Prosthetic foot: It should be: 1- Providing stable base of support. 2- Shock ubsorption. 3- Joint & musch stimulation. 4- Cosmetic appearance. Conventional: 1) Articulated: Single axis: Have a single metal axis that allows plantar (15 degree) and dorsiflexion ( 5-7 degree). Internal keel surrounded by foam-rubber outer lining. Loaded with dorsiflexion bumper that replaces eccentric contraction of plantar flexors, and plantarflexion bumper that replaces eccentric contraction of dorsiflexion. It allows level- floor ambulation but does not allow for walking on a steep incline. Multiple- axis foot: The multiple axis foot has two joints, a rubber rocker block that allows dorsiflexion and plantarflexion and a transverse ankle joint that allows rotation, eversion and inversion. It contains a wood keel and outer cover of foam rubber. It allows walking on level ground and inclines II) Non articulated The solid-Ankle Cushion-Heel Consists of wood keel that extends forwards to the toe break and is surrounded by molded foam. The SACH compressible rubber heel simulates plantar flexion. At loading response the heel wedge comprises to simulate plantar flexion. Stationary- Attachment Flexible Endoskeletal (SAFE) FOOT The SAFE foot keel, is composed of rigid polyurethane plate at an angle 45 in the sagittal plane to provide eversion and inversion. To elastic bands extend on the plantar surface that courses the keel to dorsiflex from mid- to terminal stance. At pre swing the keel releases. Stored Energy (STEN) Foot The keel is subdivided into comprisable and non compressible segments, a structure that allows energy storage from loading response to mid swing and release it at push off. Dynamic Response Feet Articulated College Park True Step Foot It has three axes one vertical and two transverse axes. These axes allow mobility in the three planes of motion. Two bumpers, dorsi- and plantar flexion bumpers are included. In front there are two split toes of carbon fibers. Non- Articulated Long keel: Flex foot: Two elastic carbon fibers attached to a horizontal carbon foot plate. Carbon fibers extend to include the pylon. Springlite Similar to flex foot, but consists of one elastic carbon fibers and one fiber glass filaments surrounded by a soft cover. It is 30% less expensive than flex foot. Short Keel Carbon Copy II Consists of two carbon fiber deflection plates that return energy during walking and running. It has a strong keel covered by polyurethane foam. Seattle Foot Has a lifelike appearance. Keel stores energy in mid- to terminal stance, and it is released at the end of the stance phase. Sockets PTB: areas of wt. bearing 1- Patellar tendon. 2- Medial flow of medial tibial condyle and antero medial shaft of residual tibia. 3- Mid shaft fibula. 4- Distal end bearing if tolerated. Non-weight bearing 1- Back & distal end fibula 2- Anterior lateral edges of lateral tibia 3- Anterior and distal tibial surface. 4- Tibial tuberosity. Total surface bearing Complete weight bearing evenly distributing pressure on the contact surface. Depends on: Patient skin condition, and residual limb condition. Suspension: 1- Supra condylar (medial wedge). 2- Supra condylar- supra patellar system. 3- Supra condylar cuff. 4- Thigh corset. 5- Waist belt. 6- Sleeve. (neoprene – wrethane – silic). 7- Shuttle – pin. Spinal Supports And Braces This group of braces can be simply classified into cervical and trunk supports. I. Trunk Supports This is further classified into supportive and corrective spinal orthoses. Supportive spinal orthoses are either made of soft fabrics and rigid spinal orthoses. I) Supportive Spinal Orthoses A) Soft Supportive Spinal Orthoses: 1) Elasticon Garment: Elasticon garment consists of a cylinder of two-way stretch materials that extends from the nipple lines to the greater trochanter. Stretch material is longer anterior than posterior. Two shoulder straps used to control downwards slide of the garment and adjust its size to subject’s size. Two thigh pieces that prevents garment to roll up, they extend mid way between hip and knee joints. Two spiroflex malleable metal bars extend paraspinally. It is helpful in: Acute, subacute, and chronic low back strain. Advanced lumbar spondylosis. Discogenic lesions. Post operative disc conditions. Elasticon garment has the advantage of reducing lumbar pain while preserving back mobility. 2) Spinal Belts And Corsets: These forms of spinal supports are the most commonly prescribed types of spinal orthoses. They are usually made of leather or cotton fabrics of different types (coutil, jean, or canavas). They are reinforced as necessary with metal strips. They are classified according to their size into sacroiliac orthoses (5-15 cm). A lumbo-sacral orthoses extend to the thoracolumbar junction (20-40cm in height). Thoracolumbar belts extends to the inferior angle of the scapula with height of more than 40 cm. Belts encircle the pelvis, abdomen, and/or lower chest according to its type. Buckles or laces tighten it anteriorly. A fulcrum strap is used to fasten and reinforce the belt. This strap passes laterally between iliac crest and greater trochanter. These forms of supports are utilized in different painful conditions of the spine. B) Rigid Supportive Spinal Orthoses: 1) Chair back supports It is made of slightly malleable metal, covered by leather or similar synthetic materials, fastened by buckles in front. The upper part of the lumbar spine is more completely immobilized than the lower. It is utilized in cases of severe painful or infectious disorders of the spine where strong support and relative immobility of the trunk. It is used 4-6 month post operatively following spinal fusion. 2) The light cast jacket spica This is made of light cast bandage. It encircles the chest and abdomen from the nipple line to the groin. One hip and one thigh are incorporated as far as the knee. This type of support is employed after all lumbar or lumbosacral spinal fusion operations and is worn for 3 months to produce the highest possible rate of fusion by almost complete immobilization. II) Corrective Spinal Orthoses 1) Milwaukee brace Milwaukee brace is an active corrective spinal orthosis, used in treatment of spinal orthosis, to prevent or postpone the need of operation. Also, it can be used post operatively. In addition it can be used in the management of ankylosing spondylitis, tuberclosis, or other infections of the upper thoracic region of the spine. It consists of leather pelvic corset that fits firmly around the pelvis. Metal sidebars are attached to the leather pelvic corset. Two posterior and one anterior upright extend from the center of these metal sidebars to a metal neck ring that takes 20 degree inclination anteriorly to avoid pressure on the throat. In addition the throat has a throat mould anteriorly. There are two occipital pads that supports the head posteriorly. Rib rotation is corrected by a pressure pad located over the rib prominence. The pressure pad is fixed to a single, broad leather strap. 2)Boston brace it is also utilized to treat lumbar and thoracolumbar scoliosis with apex of the curve below thoracic vertebra number 8. It is prefabricated from polypropelene (3mm thickness) and padded with foam (7mm thickness). It is a positive mould of normal torso, which is provided in 20 different sizes to be suitable for almost all scoliosis patients. I. Neck Collars & Supports 1) Temporary Collar A double thickness of sponge rubber or felt wrapped round the neck and enclosed within a length of tubegauz which facilitates typing. Usually sponge rubber is supplied in form of sheets (20X 40 cm). It is convenient to fold the sheets and then to trim the margins to form a chin cut out and two shoulder cut outs in upper and lower margins respectively. 2) Inflatable Rubber Collar It consists of 3 compartments, which can be inflated by a common air inlet to any desired tension. These compartments are joined by a strip of rubber, and a flange at either extremity carries laces to adjust circumference. It provides a good degree of support without skin traumas. However, its major disadvantage is lack of ventilation. 3) Sponge Rubber Collar A sheet of sponge rubber specially shaped to avoid pressure under the clavicles and the end of the chin is enclosed within an envelope of leather. This provides firmer support than an inflatable collars but again suffers from lack of ventilation. 4) Thomas Collar Made of a thermo- plastic material and padded with sponge rubber at the upper and lower margins to avoid undue pressure on the jaw and clavicles. Ventilation holes can be cut in the body of the material. 5) Victoria Collar Two strips of spring steel form seven eighths of a circle; these are suitably padded and connected together by three distance pieces, one in the center of the curve and one at each extremity. Height of distance pieces is adjustable to individual neck height. 6) Frame Collar In cases where pressure on the neck skin cannot be tolerated, or if there is neck injuries of wounds that need be supervised, frame collar can be used. Two shoulder strips of metal are curved around the shoulder. These two strips are joined together anteriorly and posteriorly at a triangular mild steel. From the posterior triangle a malleable steel upright arises from the posterior triangle and end up at an occiptal strip. Another vertical upright of malleable steel and end up by a chin cup. 7) Doll’s Collar This consists of two sheets of thermoplastic material made to a plaster cast of the upper thorax, neck and lower part of the head. A light plaster must be applied first, split down either side, removed from the patient, reassembled and used as a negative for a plaster positive, and the thermoplastic material must be molded to this. It is then split down each later margin and suitably padded, the two halves being connected by leather strips and buckles.
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