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Biomechanics of Walking for People with Lower Extremity Amputations Dave Thompson PT http://moon.ouhsc.edu/dthompso/ PowerPoint Presentation
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Biomechanics of Walking for People with Lower Extremity Amputations Dave Thompson PT http://moon.ouhsc.edu/dthompso/. Objectives. List the gait deviations that are most common in people who wear prostheses, and explain their most frequent causes.

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slide1
Biomechanics of Walking

for People with

Lower Extremity Amputations

Dave Thompson PT

http://moon.ouhsc.edu/dthompso/

Update on Lower Extremity Amputations

September 28, 2006

objectives
Objectives
  • 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 prosthetic foot alignment affects the alignment of a person's residual limb inside a prosthetic socket.

Update on Lower Extremity Amputations

September 28, 2006

when is someone ready for a prosthesis
When is someone ready for a prosthesis?
  • when he or she can control the knee joint well enough to walk safely.

Update on Lower Extremity Amputations

September 28, 2006

controlling the knee joint
Forces that affect joint position and movement during stance:

ground reaction

muscles

joint reaction

Controlling the knee joint:

Update on Lower Extremity Amputations

September 28, 2006

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.

Ground reaction force (GRF)

Update on Lower Extremity Amputations

September 28, 2006

a useful simplification moments produced by grf and muscles are equal and opposite
A useful simplification: Moments produced by GRF and muscles are equal and opposite.

Mmm = -Mgrf

Update on Lower Extremity Amputations

September 28, 2006

moments produced by grf and muscles are equal and opposite
Moments produced by GRF and muscles are equal and opposite.

During loading response, GRF’s sagittal plane location is:

  • posterior to ankle axis
  • posterior to knee axis
  • anterior to hip axis

Update on Lower Extremity Amputations

September 28, 2006

to preserve stability people with amputations can compensate for absent or weak muscles by
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.

Update on Lower Extremity Amputations

September 28, 2006

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

Controlling the knee joint during loading response:

Update on Lower Extremity Amputations

September 28, 2006

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

A less useful way to control the knee joint during loading response:

Update on Lower Extremity Amputations

September 28, 2006

prosthetic alignment can help control knee joint during loading response
Position prosthetic foot so origin of GRF is more anterior.Prosthetic alignment can help control knee joint during loading response:

Update on Lower Extremity Amputations

September 28, 2006

moments produced by grf and muscles are equal and opposite1
Moments produced by GRF and muscles are equal and opposite.

During preswing, GRFV’s sagittal plane location is:

  • anterior to ankle axis
  • posterior to knee axis
  • posterior to hip axis

Update on Lower Extremity Amputations

September 28, 2006

initiation of knee flexion during preswing
Initiation of knee flexion during preswing

GRF initiates prosthetic knee flexion if it is posterior to knee joint axis.

  • Heel must rise.
  • Pelvis must rotate forward, moving the femur.
  • Body weight must transition smoothly from trailing to forward limb.

Update on Lower Extremity Amputations

September 28, 2006

poor preswing initiation of knee flexion
Four probable causes

 GRF

 fwd pelvic rotation

 hip flexor action

Prosthetic alignment that delays heel rise.

Poor preswing initiation of knee flexion

Update on Lower Extremity Amputations

September 28, 2006

moments produced by grf and muscles are equal and opposite2
Moments produced by GRF and muscles are equal and opposite.

During loading response, GRF’s frontal plane location is:

  • lateral to subtalar axis
  • medial to knee
  • medial to hip axis

Update on Lower Extremity Amputations

September 28, 2006

hip abductors counter grf s adductor moment
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, 94-102.

http://www.oandp.org/jpo/library/1990_01_094.asp

Update on Lower Extremity Amputations

September 28, 2006

lateral trunk lean reduces grf s hip adductor moment
Lateral trunk lean reduces GRF’s hip adductor moment

Update on Lower Extremity Amputations

September 28, 2006

objectives1
Objectives
  • List the gait deviations that are most common in people who wear prostheses, and explain their most frequent causes.

Update on Lower Extremity Amputations

September 28, 2006

objectives2
Objectives
  • 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.
  • http://moon.ouhsc.edu/dthompso/gait/pobmk/frames.htm

Update on Lower Extremity Amputations

September 28, 2006