General Prosthetics Flashcards
Knee Disarticulation Amputation Types (5)
True KDA
Gritti-Stokes
Callender
Burgess
Mazet
Typical gait Pattern of Forefoot and Hindfoot Amputees (4)
Characterized by less active plantarflexion
Delayed progression of the centre of pressure
Starter stride length tendency to prematurely shift body weight to the contralateral side
Gait is wide based, slower and less energy efficient
Bench Alignment for HDA Prosthesis
Sagittal
Alignment reference line passes
-through the COR of the socket in 5 degrees anterior tilt
-posterior to the hip joint (1cm?)
-anterior to the knee joint (1cm?)
-through the weightbearing surface of the foot
Transverse
- All joint axes run parallel to each other and are perpendicular or slightly externally rotated from the LOP
- socket in LOP
Frontal
Alignment reference line passes
-through a point on the socket midway between ASIS and IT on amputated side
-through the center of the hip, knee, and heel
-pelvis, hip, knee, ankle all the parallel to the ground
HDA Biomechanics at Terminal Stance/Pre Swing
- socket tilts anteriorly (forces prox/post and distal/ant)
- force increased on hip ext stop, knee destabilizes and flexes
- GRF - post to hip, post to knee, ant to ankle
Chopart Amputation
- tarsals transected, calcaneus and talus remain
- tendency to hold a varus and equines position
- leg length discrepancy as a fit issue
- ankle movement between residuum and socket -> pressure and shear
- alignment and shoe fit
- able to distal end bear/self suspend
HDA Socket Design Principles (3)
1) Seat for vertical loading of the ischium
- along with encapsulation of the illiac crests helps control rotation
- weight bearing surface which can tolerate force
2) Lateral support of sound side illium both A and D
- keep socket snug in A/P and M/L
- allows control of the prosthesis by pelvic tilt
3) Suspension over the crest of the illium on the amputated side
KDA: External Hinges vs. Polycentric/4 bar linkage
External Hinges
- no swing phase controls
- cosmetic advantage/disadvantage
- length KC vs. Width
Polycentric
- stable
- cosmetic disadvantage
Specific Assessment requirements for Symes (5)
- size of heel pad
- degree of heel pad mobility
- tolerance to distal end pressure
- malleolar remnants
- previous distal end weight bearing
Symes Casting Techniques (4)
- circumferential wrap/longitudinal split
- obturator door
- slab
- Berkeley casting stand
HDA Biomechanics at Midstance
GRF is
-anterior to ankle COR (external dorsiflexion moment)
-anterior to knee COR (external knee extension moment)
-posterior to hip COR
(external hip extension moment)
Each joint should be locked, supporting weight without collapse (contralateral swing)
HDA Biomechanics at Initial Contact and Loading Response
GRF is -posterior to ankle COR (external plantarflexion moment) -anterior to knee COR (external knee extension moment) -through or posterior to hip COR (external hip extension moment)
Potential Socket Designs for KDA or Symes (5)
- obturator
- segmented liner (stove pipe)
- molded leather
- silicon (expandable walls)
- bivalve socket
Advantages/Disadvantages of a Symes Amputation
Advantages
- distal end weight bearing
- self suspension
- long lever arm
- increased proprioception and prosthetic control
- increased area for distribution of forces
Disadvantages
- cosmesis
- risk of heel pad hypermobility and displacment
- donning/doffing issues
- limited room for components
Lisfranc Amputation
- tarsal metatarsal level
- may see equinovarus deformity
- LLD
- decreased ROM
- short lever arm -> typically above ankle design
- suspension an issue
Problems present after amputation involving metatarsals (3)
- reduced plantar weight bearing surface
- impaired pronation/supination during gait
- loss of active push-off