Q1: Biomechanical Goals TT Flashcards

1
Q

What are the biomechanical goals of a TT Prosthesis

A
  1. Maximize residual limb weight bearing capacity
  2. maintain ML stability through stance phase
  3. maintain sagittal plane stability through stance phase
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2
Q

What are the three ways to accoomplish goal #1 (Maximize residual limb weight bearing capacity)

A
  1. total contact socket design
  2. intentional loading and socket fit
  3. flexed alignment of the socket
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3
Q

Total Contact Socket Design

A
  • increases overall surface area
  • minimizes distal end edema
  • increases proprioception
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4
Q

Pressure Tolerant Areas PTB Socket Design

A
  • Medial Tibial Flare
  • Patellar Tendon
  • Shaft of fibula
  • Anterior compartment
  • Medial Tibial Shaft
  • Medial femoral condyle
  • Popliteal Fossa
  • Distal End
  • Gastrocnemius
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5
Q

Pressure Intolerant Areas PTB Socket Design

A
  • Fibular Head
  • Peroneal Nerve
  • Crest of Tibia
  • Distal Fibula
  • Hamstring Tendons
  • Distal Anterior Tibia
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6
Q

Equal Pressure Distribution (TSB)

A
  • Impression technique without specifically applied pressures
  • modification process does not relieve specific areas
  • Use of gel liner assists in equalization of pressure
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7
Q

What does flexed alignment increase?

A
  • increases the area for vertical load bearing on the anterior surface of RL
  • Socket flexion for PTB: begin at 10 deg
  • Socket flexion for TSB: begin at 5 deg
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8
Q

What are the ways to accomplish goal #2 (maintain ML stability through stance phase)

A
  1. coronal plane alignment
  2. transverse plane alignment
  3. socket fit and stability
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9
Q

Where should GRF line pass in relation to the knee at midstance

A
  • should pass medial to knee joint at midstance
  • slight varus thrust at midstance
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10
Q

What are the general guidelines for foot inset:

A
  • short limbs: 3-6 mm inset
  • Medium limbs: 6-9 mm inset
  • Long Limbs: 9-12 mm inset
  • Bilateral patients: 0-6 mm inset
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11
Q

What are the benefits of Foot Inset/Varus Moment

Narrow base of support

A
  • provides midstance stability
  • simulates NHL (normal human locomotion)
  • Decreases energy expenditure
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12
Q

What does excessive medial placement of the foot produce

A
  • excessive varus moment
  • increased lateral distal pressure
  • increased medial proximal pressure
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13
Q

What does excess lateral placement of the foot produce

A
  • valgus moment
  • medial distal pressure
  • proximal lateral pressure
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14
Q

What happens if the socket is excessively ABducted

A
  • when patient walks, socket will follow the patients anatomical presentation
  • lateral leaning pylon, medial aspect of foot off ground, excessive varus moment
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15
Q

Increased Toe out……

A

Results in wider base of support at terminal stance

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16
Q

excessive toe out ……

A

results in a reduced varus moment OR valgus moment at terminal stance

17
Q

insufficient toe out…..

A

results in an excessive varus moment at terminal stance

18
Q

If socket does not fit snugly in ML dimension…..

A

socket will move on limb in stance phase

19
Q

Ways to accomplish goal #3 (sagittal plane stability)

A
  1. sagittal plane alignment
  2. appropriate heel/keel properties
20
Q

Heel lever goals during loading response

A
  • weight acceptance with shock absorption through heel
  • stable and controlled knee flexion
21
Q

Toe lever goals in terminal stance

A
  • sufficient forefoot leverage to maintain weight bearing until contralateral weight acceptance (long)
  • prevention of excessive knee extension moment in terminal stance (short)
22
Q

Sagittal Plane alignment goal

A

reduce knee extension moment during loading terminal stance

23
Q

What is socket position determined by

A

sagittal plane bisector at MPT level

24
Q

3 reasons for flexing the transtibial socket

A
  1. load anterior surface of RL (goal 1)
  2. increase knee flexion moment during early stance (goal 3)
  3. decrease knee extension moment during terminal stance (goal 3)
25
Q

During loading response, we want the prosthesis to replace what?

A

anatomic eccentric dorsiflexor activity

26
Q

Heel Durometer

A
  • cushioned heel of SACH foot compresses during loading response and facilitates controlled foot flat
  • simulates plantar flexion of the ankle
  • improves stability as foot fully contacts the ground
27
Q

increased heel stiffness results in ?

A

greater knee flexion moment and decreased shock absorption

28
Q

What happens if there is an excessivley soft heel

A
  • early stance phase appears delayed, like person is stuck and acannot roll forward onto the foot
  • “stepping into a hole”
  • knee will remain in extension
29
Q

Keel properties goals in terminal stance

A
  • sufficient forefoot leverage to maintain weight bearing until contralateral weight acceptance
  • prevention of excessive knee extension moment in terminal stance
  • affected by: length of keel, flexibility of keel