Biomechanics of Prosthetic Use Flashcards Preview

Amputation and Prosthetics > Biomechanics of Prosthetic Use > Flashcards

Flashcards in Biomechanics of Prosthetic Use Deck (55)
Loading flashcards...

weightbearing in a prosthetic socket should be distributed where?

pressure tolerance areas


list pressure tolerance areas for transtibial prosthesis

  1. patellar tendon
  2. pretibials
  3. posterior distal aspect of residual limb
  4. popliteal fossa
  5. lateral shaft of fibula and tibial flares



Avoid putting pressure on ______ areas



define bench alignment

how the prosthesis is set up/factory setup


in order to have M/L stabilization for transtibial prosthesis, what occurs during bench alignment?

attempt to replicate the normally occuring varus at the knee

by placing foot 1/2 inch medial to center 


why should we want to replicate the varus at the knee for a transtibial prosthesis?

if the residual limb moves into valgus positoin in the socket it can result in pressure at the fibular head and peroneal nerve


how is A/P stabilization achieved in a transtibial prosthesis?

  1. place the socket in 5º flexion to enhance patellar tendon bearing (PTB)
  2. place foot slightly posterior to center of socket


describe 2 incorrect placements for transtibial prosthesis

  1. too far anterior → excessive anteroproximal and prosteriodistal pressure
  2. too far posterior → hyperflexion at the knee with excessive posterioproximal and anteriodistal pressure



how can you correct a TT foot outset?

translate the socket laterally or translate the foot medially


where would pressure from the socket be most felt in a TT foot oustet position?

(foot will be more lateral)

lateral superior lip of socket (proximal lateral)

 and medial base (distal medial) of the socket 


how can you correct a TT foot inset?

translate foot laterally or translate socket medially


where would pressure from the socket be most felt in a TT foot inset?

superior medial lip of socket

and lateral inferior edge of socket 


having a TT socket anterior is the same as saying what?

the foot is too far posterior


where would pressure be applied the most on the socket in a TT socket anterior?

superior posteriorly behind the "knee"

base anterior portion 


what 3 things should be kept in mind when considering transfemoral amputees biomechanics?

  1. minimize rotation of socket
  2. M/L stability
  3. sagittal plane stability



why is minimizing rotation of the socket a unique issue for a transfemoral prosthesis?

a transfemoral prosthesis is more like a round cylinder on a round peg and is very fleshy which can move a lot more than a TT which is more like a rectangle and gets good purchase of the prosthesis on the limb and doesn't rotate a lot due to the bony angles 


how can you minimize rotation of the socket in TFA?

  1. maintain pelvis position in a posterior tilt on posterior rim
  2. incorporate ischial/gluteal weightbearing
  3. adductor longus tendon housed in a groove



what 4 points will allow greater M/L stability in a TF prosthesis?

  1. need good lateral wall support (often make it slanted)
  2. provide abductor contact with the socket
  3. points of force in proximomedial direction and distolateral direction to prevent lateral shifting in socket
  4. center of heel under or slightly lateral to ischial tuberosity to promote slight valgus



why would we want to promote valgus in a TF prosthesis?

aids in M/L stabilization 

promotes a Trendenlberg like gait and takes pressure off the medial socket/groin region


describe 2 incorrect foot placements for TF prosthesis

  1. foot too far medial (most likely) → excessive pressure in groin and distolateral
  2. foot too far lateral → excessive pressure proximolateral and distomedial



how is sagital plane stability achieved in a TF prosthesis?

GRF must remain anterior to the knee joint

this is achieved by having 5º flexion built into the socket (at the hip)

this enhances glute firing (and efficiency) and helps avoid hyperlordosis



define static checkout

looking for basic fit principles in a prosthesis


define dynamic checkout

assessing prosthesis during gait


list things included in a static checkout

  1. soles of feet are flat
  2. socket fits well
  3. user comfortable
  4. is suspension adequate?
  5. ensure bony landmarks are level (bilaterally)
  6. vertical pylon in stance
  7. minimize tissue rolls
  8. gapping between leg and socket
  9. does residuum have distal contact? (think plato)
  10. normal heel center spacing
  11. is the knee stable?



Define end-bearing socket

when the residuum bears weight at the distal aspect


define suspension

the means of holding the socket on the residuum


list pressure sensitive areas in a TT socket

  1. cut ends of the bones
  2. tibial crest and tuberosity
  3. fibular head
  4. tibial condyles
  5. distal hamstring tendons



List 2 socket designs used in TTA

  1. PTB - patellar tendon bearing
  2. TSB - total surface bearing



what is a TSB (total surface bearing) socket?

the entire limb contacts the socket, weight bearing is biased to pressure tolerant areas.

In a TSB socket there is nonspecific loading with minimal bony reliefs

usually use a gel liner


list the 2 methods used to measure someone for a socket

  1. casting (older method)
  2. computerized scan CAD/CAM of person's limb