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Updated: Jun 17 2021

Rehab & Prosthetics

3.6

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(46)

Images
https://upload.orthobullets.com/topic/9072/images/bodypowered.jpg
https://upload.orthobullets.com/topic/9072/images/myoelectric.jpg
https://upload.orthobullets.com/topic/9072/images/myoelectric2.jpg
https://upload.orthobullets.com/topic/9072/images/bodypowered2.jpg
https://upload.orthobullets.com/topic/9072/images/polycentricknees.jpg
  • Introduction
    • The goal of prosthetics are to restore limb function to as close to original function
    • Requires a multidisciplinary team approach for coorindation of efforts to achieve the best outcome
    • Prosthetics
      • upper limb
        • limb salvage is ideal in the upper arm given lack of sensation with prosthetic
        • residual limb length is important for suspending prosthetic socket
      • lower limb
        • goals for prosthetic are comfort, easy to get on and off, light, durable, cosmetic, and functional
  • Gait
    • Antalgic gait describes any gait abnormality resulting from pain
      • shortened stance phase on the affected limb
    • Gait pattern of ambulation with an assistive device
      • 3-point
        • both the crutch and the injured limb move forward together with weight-bearing on the crutches followed by all of the weight on the uninjured limb
      • 4-point
        • first one crutch is advanced, then the opposite leg, then the second crutch, then the second leg, and so on
      • swing-to
        • that in which the crutches are advanced and the legs are swung to the same point
      • swing-through
        • that in which the crutches are advanced and then the legs are swung past them 
    • Crutch walking
      • requires more energy than walking with a prosthesis
      • muscles that need strengthening in preparation for crutch walking
        • latissimus dorsi
        • triceps and biceps
        • quads
        • hip extensors
        • hip abductors
    • Wheelchair propulsion
      • 9% increase in energy expenditure compared to ambulation in normal subjects
    • Ambulation assistive devices
      • cane
        • shifts center of gravity towards affected side when cane is used on contralateral side
      • axillary crutch
        • 2 axillary crutches are required for proper gait if lower extremity is non weight-bearing or toe-touch weight-bearing
  • Upper Extremity Prostheses
    • Timing of prosthetic fitting
      • as soon as possible, even before complete wound healing has completed
        • better outcomes if fitted within 30 days
    • Midlength transradial amputation
      • Myoelectric prostheses
        • best candidate is a patient with a midlength transradial amputation
        • transmits electrical activity to surface electrodes on residual limb muscles
        • advantages
          • better cosmesis
          • allows more proximal coverage
        • disadvantages
          • heavier and more expensive prosthesis
          • requires more maintenance
      • Body-powered prostheses
        • indications
          • best for heavy labor with less maintenance needed
        • techniques
          • activate terminal device with shoulder flexion and abduction
          • center the harness ring just off the midline of C7 towards the non-amputated side
        • advantages
          • moderate cost and weight
          • most durable prosthesis
          • higher sensory feedback
        • disadvantages
          • poorer cosmesis
          • requires more gross upper limb movement for proper function
    • Elbow disarticulation or above elbow amputation
      • requires a prosthesis to recreate functional motion of two joints (elbow and wrist)
        • this creates heavy and less efficient as the only solution
        • best function with least weight is achieved by combining the various options of myoelectric, body-powered, and body-driven switch components
    • Proximal transhumeral and shoulder disarticulation amputation
      • an amputation this proximal has lost the ability to create a lever arm with mechanical advantage
      • best option is a universal shoulder joint that is positioned in space with the contralateral arm
      • this can be combined with lightweight hybrid prosthetic components
    • Components
      • Terminal device
        • passive terminal device
          • more cosmetic but less functional than active terminal devices
        • active terminal device
          • more functional, but less cosmetic than passive terminal devices
          • either hooks and prosthetic hands with cables or myoelectric devices
        • grips
          • precision grip (pincer-type)
          • tripod grip (palmar grip, 3-jaw chuck pinch)
          • lateral pinch (key pinch)
          • hook power grip
          • spherical grip
        • prehension devices
          • handlike device
            • thumb, index, and long finger components
            • may be covered with a glove for better cosmesis
            • good choice for office worker
          • non-hand prehension device
            • hook or two-finger pincer with parallel surfaces
            • may attach task-specific tools with quick release mechanism
            • good for physical labor
          • myoelectric devices
            • can only be used in an environment clean from dirt, dust, water, grease, or solvents
        • mechanisms
          • voluntary opening
            • device is closed at rest and opens with contraction of proximal muscles
            • more common than voluntary closing
          • voluntary closing
            • device is open at rest and residual forearm flexors grip the desired object
            • heavier and less durable than voluntary opening
      • wrist units
        • quick disconnect wrist
          • allows easy swapping of devices with specialized function
        • locking wrist unit
          • prevents rotation during grasping and lifting
        • wrist flexion unit
          • used in bilateral upper extremity amputees
          • placed on longer residual limb to allow midline activities (shaving, buttoning)
      • elbow units
        • rigid elbow hinge
          • indications
            • short trans-radial amputation with inability to pronate or supinate with maintenance of elbow flexion
        • flexible elbow hinge
          • indications
            • wrist disarticulation or long transradial amputation with sufficient pronation, supination, and elbow flexion and extension
      • shoulder units
        • due to increased energy expenditure and weight of prosthesis many choose to use a purely cosmetic prosthesis
        • indications
          • forequarter or shoulder level amputation
  • Lower Limb Prosthesis
    • Foot prosthesis
      • Single axis foot
        • ankle hinge allows dorsiflexion and plantar flexion
        • disadvantages
          • poor durability and cosmesis
      • SACH (solid ankle cushioned heel) foot
        • indications
          • general use in patients with low activity levels
          • use is being phased out
        • disadvantages
          • overloads the nonamputated foot
      • Dynamic response (energy-storing) foot
        • indications
          • general use for most normal activities
          • patients who regularly ambulate over uneven surfaces likely benefit from multi-axial articulated prostheses
        • articulating and non-articulating dynamic-response foot prostheses are available
          • articulating
            • allows inversion, eversion, and rotation of the foot
            • indications
              • patients walking on uneven surfaces
            • advantages
              • allows inversion, eversion, and foot rotation
              • absorbs loads and decreases shear forces
              • flexible keels
                • acts as a spring to decrease contralateral loading, allow dorsiflexion, and provide a spring-like push-off
                • posterior projection from keel gives a smooth transition from heel-strike
                • sagittal split allows for inversion and eversion
          • non-articulating
            • have short or long keels
              • shorter keels are not as responsive and are indicated for moderate-activity patients
              • longer keels are indicated for high-demand patients
            • different feet for running and lower-demand activities available
      • Shanks
        • provide structural support between components
        • endoskeleton (soft exterior) or exoskeleton model (hard exterior)
        • can provide a lever arm for propulsion following transmetatarsal amputation
    • Knee prosethesis
      • Indications
        • transfemoral and knee disarticulation amputations
        • patient functional status is an important consideration
      • Six types of prostheses for AKA or through knee
        • polycentric (four-bar linkage) knee
          • indications
            • transfemoral amputation
            • knee disarticulations
            • bilateral amputations
          • techniques
            • variable knee center of rotation
            • controlled flexion
            • ability to walk at a moderately fast pace
            • supports increased weight compared to constant friction knee
        • stance-phase control (weight-activated) knee
          • indications
            • older patients with proximal amputations
            • patients walking on uneven terrain
          • techniques
            • acts like a constant-friction knee in swing phase
            • weightbearing through the prosthesis locks up through the high-friction housing
        • fluid-control (hydraulic and pneumatic) knee
          • indications
            • active patients willing to sacrifice a heavier prosthesis for more utility and variability
          • techniques
            • allows for variable cadence via a piston mechanism
            • prevents excess flexion
            • extends earlier in the gait cycle
        • constant friction (single axis) knee
          • indications
            • general use
            • patients walking on uneven terrain
            • most common pediatric prosthesis
            • not recommended for older or weaker patients
          • technique
            • hinge that uses a screw or rubber pad to apply friction to the knee to decrease knee swing
            • only allows a single speed of walking
            • relies on alignment for stance phase stability
        • variable-friction (cadence control)
          • technique
            • multiple friction pads increase knee flexion resistance as the knee extends
            • variable walking speeds are allowed
            • not very durable
        • manual locking knee
          • technique
            • constant friction knee hinge with an extension lock
            • extension lock can be unlocked to allow knee to act like a constant-friction knee
    • Socket
      • the connection between the stump and the prosthesis
      • computer screening technology can decrease time to socket fabrication
      • preparatory socket may need to be adjusted several times as edema resolves
      • patellar tendon-bearing prosthesis is most common for BKA
      • transfemoral or quadrilateral sockets make it hard to keep the femur in adduction
        • transfemoral allow 10 degrees of adduction and 5 degrees of flexion
    • Suspension systems
      • attaches prosthesis to residual limb using belts, wedges, straps, and suction
      • suction suspension
        • standard suction
          • form-fitting rigid or semi-rigid socket which fits onto residual limb
        • silicon suction
          • silicon-based sock fits over the stump and is then inserted into the socket
          • silicon provides an airtight seal between prosthesis and amputated stump
    • Pylon
      • simple tube or shell that attaches the socket to the terminal device
      • newer styles allow axial rotation and absorb, store, and release energy
      • exoskeleton
        • soft foam contoured to match other limb with hard outer shell
      • endoskeleton
        • internal metal frame with cosmetic soft covering
    • Osseointegration
      • direct attachment of a prosthesis to the skeleton
      • may improve biomechanical advantage of prosthesis and rehabiliation
    • Terminal device
      • Most commonly a foot, but may take other forms
  • Prosthetic Complications
    • General issues
      • choke syndrome
        • caused by obstructed venous outflow due to a socket that is too snug
        • acute phase
          • red, indurated skin with orange-peel appearance
        • chronic phase
          • hemosiderin deposits and venous stasis ulcers
      • skin problems
        • contact dermatitis
          • most commonly caused by liner, socks, and suspension mechanism
          • treatment
            • remove the offending item with symptomatic treatment
        • cysts and excess sweating
          • signs of excess shear forces and improperly fitted components
        • scar
          • massage and lubricate the scar for a well-healed incision
      • painful residual limb
        • possible causes include heterotopic ossification, bony prominences, poorly fitting prostheses, neuroma formation, and insufficient soft tissue coverage
    • Transtibial prostheses
      • swing-phase pistoning
        • ineffective suspension system
      • stance-phase pistoning
        • poor socket fit
        • stump volume changes (stump sock may need to be changed)
      • foot alignment abnormalities
        • inset foot (medialized)
          • varus strain, circumduction and pain
        • outset foot (lateralized)
          • valgus strain, broad-based gait and pain
        • anterior foot placement
          • stable increased knee extension with patellar pain
        • posterior foot placement
          • unstable increased knee flexion
          • drop-off or knee buckling can be improved by moving the foot more anterior
        • dorsiflexed foot
          • increased patellar pressure
        • plantar-flexed foot
          • drop-off and increased patellar pressure
      • pain or redness related to pressure
      • prosthetic foot abnormalities
        • heel is too soft
          • leads to excessive knee extension
        • heel is too hard
          • leads to excessive knee flexion and lateral rotation of toes
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