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Update on Lower Extremity Amputations September 28, 2006 1 Biomechanics of Walking for People with Lower Extremity Amputations Dave Thompson PT

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Presentation on theme: "Update on Lower Extremity Amputations September 28, 2006 1 Biomechanics of Walking for People with Lower Extremity Amputations Dave Thompson PT"— Presentation transcript:

1 Update on Lower Extremity Amputations September 28, Biomechanics of Walking for People with Lower Extremity Amputations Dave Thompson PT

2 Update on Lower Extremity Amputations September 28, Objectives List the gait deviations that are most common in people who wear prostheses, and explain their most frequent causes.List the gait deviations that are most common in people who wear prostheses, and explain their most frequent causes. Explain how changes in prosthetic alignment alter the position of the ground reaction force and affect prosthetic joint movement during gait.Explain how changes in prosthetic alignment alter the position of the ground reaction force and affect prosthetic joint movement during gait. Explain how prosthetic foot alignment affects the alignment of a person's residual limb inside a prosthetic socket.Explain how prosthetic foot alignment affects the alignment of a person's residual limb inside a prosthetic socket.

3 Update on Lower Extremity Amputations September 28, When is someone ready for a prosthesis? when he or she can control the knee joint well enough to walk safely.when he or she can control the knee joint well enough to walk safely.

4 Update on Lower Extremity Amputations September 28, Controlling the knee joint: Forces that affect joint position and movement during stance: ground reaction muscles joint reaction

5 Update on Lower Extremity Amputations September 28, Ground reaction force (GRF) GRF is equal in magnitude and opposite in direction to sum of gravitational and inertial forces Assess GRF’s effect on joint movement in customary way, by evaluating its location with respect to joint axis.

6 Update on Lower Extremity Amputations September 28, A useful simplification: Moments produced by GRF and muscles are equal and opposite. M mm = -M grf

7 Update on Lower Extremity Amputations September 28, Moments produced by GRF and muscles are equal and opposite. During loading response, GRF’s sagittal plane location is: During loading response, GRF’s sagittal plane location is: posterior to ankle axisposterior to ankle axis posterior to knee axisposterior to knee axis anterior to hip axisanterior to hip axis

8 Update on Lower Extremity Amputations September 28, To preserve stability, people with amputations can compensate for absent or weak muscles by: 1. substituting another muscle in a closed chain 2. moving joint axis to  GRF’s moment about joint. 3. moving GRF to  its moment about joint.

9 Update on Lower Extremity Amputations September 28, Controlling the knee joint during loading response: People with amputations can activate muscles to control residual and prosthetic joints: Knee extensors (in TT prosthesis) Hip extensors Hip abductors / rotators

10 Update on Lower Extremity Amputations September 28, A less useful way to control the knee joint during loading response: reposition knee joint axis posteriorly to  GRF’s moment about joint by posterior rotation of pelvis

11 Update on Lower Extremity Amputations September 28, Prosthetic alignment can help control knee joint during loading response: Position prosthetic foot so origin of GRF is more anterior.

12 Update on Lower Extremity Amputations September 28, Moments produced by GRF and muscles are equal and opposite. During preswing, GRFV’s sagittal plane location is: During preswing, GRFV’s sagittal plane location is: anterior to ankle axisanterior to ankle axis posterior to knee axisposterior to knee axis posterior to hip axisposterior to hip axis

13 Update on Lower Extremity Amputations September 28, Initiation of knee flexion during preswing GRF initiates prosthetic knee flexion if it is posterior to knee joint axis. GRF initiates prosthetic knee flexion if it is posterior to knee joint axis. Heel must rise.Heel must rise. Pelvis must rotate forward, moving the femur.Pelvis must rotate forward, moving the femur. Body weight must transition smoothly from trailing to forward limb.Body weight must transition smoothly from trailing to forward limb.

14 Update on Lower Extremity Amputations September 28, Poor preswing initiation of knee flexion Four probable causes  GRF  fwd pelvic rotation  hip flexor action Prosthetic alignment that delays heel rise.

15 Update on Lower Extremity Amputations September 28, Moments produced by GRF and muscles are equal and opposite. During loading response, GRF’s frontal plane location is: During loading response, GRF’s frontal plane location is: lateral to subtalar axislateral to subtalar axis medial to kneemedial to knee medial to hip axismedial to hip axis

16 Update on Lower Extremity Amputations September 28, Hip abductors counter GRF’s adductor moment Figure from Gottschalk et al. (1989). Does socket configuration influence the position of the femur in above- knee amputation? Journal of Prosthetics and Orthotics, 2, Figure from Gottschalk et al. (1989). Does socket configuration influence the position of the femur in above- knee amputation? Journal of Prosthetics and Orthotics, 2, asp 094.asp 094.asp 094.asp

17 Update on Lower Extremity Amputations September 28, Lateral trunk lean reduces GRF’s hip adductor moment

18 Update on Lower Extremity Amputations September 28, Objectives List the gait deviations that are most common in people who wear prostheses, and explain their most frequent causes.List the gait deviations that are most common in people who wear prostheses, and explain their most frequent causes.

19 Update on Lower Extremity Amputations September 28, Objectives Explain how changes in prosthetic alignment alter the position of the ground reaction force and affect prosthetic joint movement during gait.Explain how changes in prosthetic alignment alter the position of the ground reaction force and affect prosthetic joint movement during gait. Explain how prosthetic foot alignment affects the alignment of a person's residual limb inside a prosthetic socket.Explain how prosthetic foot alignment affects the alignment of a person's residual limb inside a prosthetic socket.


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