AK Prosthetics Flashcards
Severing the adductor magnus attachment results in what % loss of adductor strength
70%
More time is spent on which side during TF gait
Sound side
How does walking speed in TF compare to TT
TF < half speed of TT
AMP Pro correlates with what
K level
Most common cause of TF amputation
Vascular
Benefits of a longer limb
Better control, suspension, and less gait deviations/energy
Benefits of KD
Longer lever arm
Self suspending
Adductor magnus preserved
Limited distal WB
No need for IC
Less EE (between TT and TF)
Disadvantages of KD
Cosmesis - bulbous end, knee centers don’t match
Limited component options
Candidates for KD
Active individuals w/o cosmetic concerns
Pediatrics
Benefits of KD vs TF in pediatrics
Reduces issues with bony overgrowth
Preserves length and growth plates
(Growth plates can be fused yo allow TF length with KD function)
Which muscle groups are severed in TF amputation? Which are rarely impacted?
Severed: quads, hamstrings, adductors
Hip flexors and abductors are more proximal
Which muscles stabilize the pelvis in SLS
Hip abductors (gluteus medius and minimus)
Common gait pattern in TF gait
Reverse trendelenburg (lateral lean) moves the COM over BoS so abductors don’t have to work as hard
What surgical technique can help stabilize the femur
Myodesis - adductors are attached laterally through femur
Benefits and indications for OI
Eliminates socket
For patients w/persistent socket and/or skin issues
Van Nes Rotationplasty common etiology
Osteosarcoma of the femur
Describe van nes rotationplasty, pros, cons
Foot and ankle rotated 180 deg so Ankle PF=knee Extension
Pro - functional
Con - cosmesis, can derotate
Two considerations in pediatric amputation
Preserve as much length as possible
Preserve growth plates to avoid bony overgrowth
Goals after TF amputation
Prevent contractures (hip flex and abd)
Reduce pain, edema, bulbous DE
Promote strength, balance, control
Prepare for prosthesis (desensitize and improve bed mobility)
Strategies to prevent contracture after TF amputation
No pillow under leg
Lie prone (if not overweight)
Extend limb off edge of bed
No pillow between legs
Issues w/shrinkers
Suspension due to shape
Lots of soft tissue
Encompass hip joint
Toileting/hygiene
What suspension options are available for an IPOP
Suspenders or belt
What motion provides voluntary prosthetic knee stability
Hip extension (effectiveness depends on surgical technique)
Boundaries of femoral / Scarpa’s triangle
Inguinal ligament, sartorius, adductor longus tendon
Which muscle group stabilizes the femur in the coronal plane
Hip Adductors
Many adductors attach to which bony landmark
Pubic ramus
Types of foam covers for AK
Continuous and discontinuous (gap at knee)
Drawback of continuous foam cover
Wrinkles behind knee and stretches on front of knee
Limitations of foam covers
Resistance to knee flexion
Tears, compression/degradation
Visual gaps
Hygiene
Skin can increase cost and is prone to punctures
Socket size relative to limb for skin fit suspension
Socket slightly smaller than limb so soft tissue compressed against socket for an air tight seal
Donning skin fit socket
One way air valve prevents air-in, can be release for doffing
Use pull sock, ace wrap, or quick dry lubricant (wet fit) for donning
Skin fit pros/cons
Least amount of pistoning, better proprioception, feels lighter, no straps or belts required
Difficult to don, hot, requires consisten RL volume
Skin fit indications
Stable RL volume
Long RL w/good skin
Good UL function
Types of suction suspension
Skin fit
Seal-in liner
Liner suspension indications
Most patients
Easier to don than skin fit
Skin reactions most common cause
Hygiene
Potential cause of discomfort w/liner
Skin traction distally
Pros/cons liner
Effective, easy to don, reduces shear, can accommodate volume changes
Less rotational control (lanyard can help), added bulk/weight/cost/length
Types of liner suspension
Lanyard
Pin lock
Seal-in
Types of strap suspension
Silesian belt / TES belt
Shoulder suspenders
Silesian belt / TES pros/cons
Common auxiliary suspension, additional rotational control, may improve adduction
Increases donning time, encircles waist (toileting inconvenience, etc)
Shoulder suspenders indications
Previously satisfied user, nothing else will work (eg. Need to reduce forces around pelvis or severe abdominal scarring)
Shoulder elevation can extend prosthetic knee
Cumbersome
Type of hip joint used for suspension
Single axis, laminated into socket and attaches to pelvic band
Location of pelvic band
1/2 way between trochanter and iliac crest
Typical interface used with hip joint and pelvic band
Sock fit
Hip joint and pelvic band indications
Max ML stability required (weak abductors, extremely short RL), previously satisfied user
Hip joint and pelvic band cons
Bulky, heavy, restricts abd/add (sit to stand, exiting car), pistoning in swing
What is the effect of total contact
Reduces distal end edema which can progress to verrucous hyperplasia and cancer if untreated
What is the effect of not fully accommodating hip extension ROM (flexion contracture)
Short step on sound side due to prosthetic side not being able to extend hip further in terminal stance
Can also create knee instability or postural changes (excessive lordosis, forward lean)
Trim lines of TF socket tend to be higher on which walls
Anterior and lateral tend to be higher
Types of TF sockets
Quadrilateral
Ischial containment
Sub-ischial
Shape of quad socket
Rectangular with 4 defined walls
Narrow AP
Where is the ischium located in quad socket
IT sits on top of posterior shelf/brim
~1” from medial wall
Shape of IC socket
Triangular cross section
Narrow ML
Shape of sub-ischial socket
Round, ischium does not contact brim
Typically elevated vacuum
Sub-ischial socket pros/cons
Comfort, hip ROM
May not contain tissue, provide ML stability, or accommodate volume changes
Quad socket limitations
Excessive brim pressures
Limited ML stability
If quads are not accommodated in socket, what will happen when they activate
Muscle activation will cause socket rotation if channel is too shallow or not acommodated
Orientation of medial wall in quad socket
In LOP
Posterior brim in quad socket is oriented in what relation to the ground
Parallel
Quad socket indications
Long, firm RL with firm adductor musculature
Previous satisfied users
What happens if medial soft tissue is not contained
Adductor roll
Consideration for the height of the anterior wall
Follow inguinal crease, should not impede hip flexion
Avoid pinching or pubic impingement when arising from chair
Shorter limbs will require higher trim line
What helps maintain IT location in socket (IT counterforce)
Anterior wall pressure (scarpa’s)
Excessive pressure in Scarpa’s triangle may cause what
Numbness from excessive pressure on nerve bundle
Orientation of lateral wall in quad socket
In LOP, flat
Function of lateral wall in socket
Stabilize femur in coronal plane
Potential gait causes of pain at distal lateral femur
Abducted gait
Trunk lean
Burning of hamstrings while seated may be due to what
Undercut of posterior wall, radius too tight, posterior shelf too wide
IC socket axial support accomplished via 3 methods
Ischial support
Gluteal support
Hydrostatic support
Inadequate IT support may result in
Ramus pressure, discomfort (slide too far into socket)
What type of support is key for shorter RL: ischial, gluteal, or hydrostatic
Gluteal - short limbs lack surface area for loading and hydrostatic pressure
More proximal or more aggressive shelf = more gluteal loading
How is hydrostatic support achieved
Volume reduction of socket relative to limb
Primary vertical WB in quad vs IC
Quad: ischial shelf
IC: combination of ischial, gluteal, and hydrostatic support
Boundaries of sub ischial triangle
Inferior pubic ramus
Semitendinosus
Gracilis
Relief in anteromedial corner of socket is for
Adductor longus tendon
Adductor longus attaches to what
Pubis
IT counterforce in IC socket
Contour and compression of rectus femoral in anterior wall
Scarpa’s pressure
Rectus channel can help control/prevent what
Rotation by allowing room for functioning muscles
Orientation of medial wall in IC socket
Internally rotated relative to the LOP
What function does the internal rotation of the medial wall serve
Precompresses the adductors to facilitate early stance phase loading and prevents lateral shifting of socket
Sub ischial triangle compresses what
Adductor musculature
Potential causes of adductor roll
Tight socket or inadequate flaring
Tissue not contained
Feature of medial brim relieves what
Ramus relief
IT is inside socket and pubis is outside socket, the ramus connects the two
Orientation of lateral wall in IC socket
Externally rotated relative to LOP
What function does external rotation of the lateral wall serve
Applies pressure to the femur in stance for ML and femur stability (help keep in adduction)
Inward angulation of socket proximal to trochanter is called
What is the function
Cupping
Reduces gapping in midstance
Is quad socket considered ischial containment
No, ischium is not contained within socket
Ischial containment can assist with what type of stability
ML stability
Purpose of aligning socket in flexion
Allows for even step length on sound side
Puts hip extensors on stretch and therefore at a functional advantage
Purpose of aligning socket in adduction
Allows for loading of lateral femur
Puts hip abductors on stretch and therefore at a functional advantage
Places femur in anatomical alignment to help stabilize pelvis
