Gait implications for Prosthetics and orthotics Flashcards
ankle-knee interaction: stance
- static stance: ankle position indirectly controls knee position
- DF ankle: GRF vector posterior to knee axis-flexion moment at knee
- with PF ankle: GRF vector anterior to knee axis- extension moment at knee strengthen HS
GRF AFO
- ankle can dorsiflex: GRF vector posterior to knee axis creates flexor moment
- ankle held in neutral: GRF vector anterior to knee axis - creates extensor moment
Biomechanical Objectives of transtibial prostheses
- Maximize WB
- improve medial/lateral stability
- encourage knee flexion
Biomechanical Objectives of transtibial prostheses
Maximize WB
- distribute forces to pressure tolerant areas (patellar tendon, medial tibial flare)
- to pressure-sensitive areas (tibial crest)
- set socket in flexion
Biomechanical Objectives of transtibial prostheses
improve medial/lateral stability
- inset prosthetic foot (medial to knee) to mimic slight knee varus at midstance
- more lateral to knee = knee valgus
Biomechanical Objectives of transtibial prostheses
encourage knee flexion
- move prosthetic socket anterior in relation to foot
- use firm heel bumper
- SACH: solid ankle cushioned heel to give some DF/PF motion
Biomechanical Objectives of transfemoral prostheses
- full, comfortable WB on residual limb
- medial/lateral stability of hip/pelvis during stance
- A/P knee stability during stance
- Permit normal step length with non amputated limb
- control of prosthetic knee during swing
Biomechanical Objectives of transfemoral prostheses
full comfort weight bearing on residual limb
- total contact force distribution
Biomechanical Objectives of transfemoral prostheses
Medial/lateral stability of hip and pelvis during stance
design features
Design features:
- inset prosthetic foot
- lateral wall of socket adducted
- narrow medial/lateral dimension of socket to stabilize femur
Biomechanical Objectives of transfemoral prostheses
Anterior/posterior stability during stance
knee joint set posterior to GRF vector
Biomechanical Objectives of transfemoral prostheses
permit normal step length with non-amputated limb
- socket set in slight flexion
- decreases amount of hip extension needed in non-amputated limb to take full step on prosthetic side
Biomechanical Objectives of transfemoral prostheses
control of prosthetic knee during swing
- want knee to flex in early swing, then extend fully in preparation for heel strike during late swing
- depends on gait speed, type of knee
excess knee flexion: initial contact into loading response (step off)
- foot goes to foot flat quickly into excess knee flexion during early stance
- transtibial prosthesis: socket in too much flexion, heel bumper too frim
- ankle-foot orthosis: solid ankle to heel rocker for bottom shoe
excess knee extension midstance to terminal stance
- transtibial prosthesis: socket not flexed enough, heel bumper too soft => delays tibial advancement
- ankle-foot orthosis: ankle permits plantarflexion => knee can hyperextend
transtibial prosthetic sock issues
too many ply
residual limb not seated down into socket
findings:
- too long on prosthetic side (iliac crest heights)
- redness below patellar tendon
- may see pistoning
transtibial prosthetic sock issue
insufficient ply
residual limb too far down in socket
findings:
- discomfort distal end of tibia
- redness above patellar tendon
- may see pistoning
Transfemoral gait deviations:
lateral trunk bending
- during stance on affected side
prosthetic causes
- prostheisis too short
- lateral wall of socket not stabilizing femur: insuffcient hip abductor torque
- medial wall of socket too high: lateral trunk bend to decrease medial pressure
Patient causes
- hip abductor weakness
Transfemoral gait deviations:
abducted gait
- during stance on affected side
Prosthetic causes:
- prosthesis too long
- medial wall of socket too high
Patient causes:
- hip abductor weakness => increase BOS => no need to stabilize pelvis
Transfemoral gait deviations:
circumduction
- during swing on affected side
prosthetic causes:
- prosthetic too long
- prosthetic foot in PF
- insufficient suspension
- medial shelf too high
- excess knee friction (transfemoral)
Patient causes:
- inability to shorten leg for swing
Transfemoral gait deviations:
vaulting
-
- during stance on unaffected side
prosthetic causes:
- prosthesis is too long
- prosthetic foot in PF
- insufficient suspension
- medial shelf too high
Patient causes:
- inability to shorten leg for swing
Transfemoral gait deviations:
uneven step length
short step on affected side
- short step on affected side
prosthetic causes:
- socket in excess flexion
- pistoning
- excess knee fricition
Patient causes
- ineffective swing affected leg
Transfemoral gait deviations:
uneven step length
short step on unaffected side
prosthetic causes:
- socket in insuffcient flexion
- prosthetic foot in PF
patient causes:
- inability to achieve hip extension during terminal stance on affected side
- spasticity ankle PF => restricts forward inclination of tibia
Transfemoral gait deviations:
uneven heel raise
prosthetic cause
- insufficient knee friction
Patient cause:
- weakness knee flexors
- spasticity knee and ankle extensors
Transfemoral gait deviations:
rotation of prosthetic foot at initial contact
- heel cushion too hard
- foot set in excess ER
- especially with Transfemoral
Transfemoral gait deviations:
Terminal swing impact
- insufficient knee friction
Lateral whip
- occurs during swing on prosthetic limb
- knee joint axis aligned in excessive internal rotation
Transfemoral gait deviations:
foot slap
- soft heel bumper
- prosthetic foot set in PF
