Lecture 10: Lower Extremity Prosthetics Flashcards
partial foot and toe amputations are common in what populations
those with dysvascular disease and/or diabetes
functional deficits for minor LE amputations (toes, great toe, ray, MTP and proximal)
toe = minor gait abnormalities
great toe = loss of push off
ray = decreased gait speed, limited LE ROM
MTP and proximal = decreased stability, decreased gait speed, and other gait deviations
what is a syme’s amputation/ankle disarticulation and type of prosthetic used
heel pad attached to distal end of tibia
may include removal of malleoli
complicated prosthetic fit due to limited space
can ambulate without prosthesis
ideal length for transtibial/below knee amputation
ideal length = mid tibia
- if <9 cm should consider removing fibula
if < 5 cm should consider knee disarticulation
fibula should be 0.5-1 cm shorter than tibia for prosthetic fit
what is a knee disarticulation
uneven functional knee joint centers
distal femur can bear weight
what is a hemipelvectomy
resection of part of the pelvis
common due to cancer or trauma
what is a hip disarticulation
amputation through hip joint
pelvis remains intact
what are k levels used for
to assess pts potential for functional ability
determines reimbursement for componentry
what is a K0 or K level 0
does not have ability or potential to ambulate or transfer safely with or without assistance and prosthesis does not enhance their quality of life or mobility
- cognitive ability insufficient
- prosthesis does not improve mobility or transfer ability
- wheelchair dependent
- bedridden + no need/capacity to ambulate/transfer
describe K level 1
ability or potential to use prosthesis for transfers or ambulation on level surfaces; typically limited to household ambulator
- sufficient cognitive ability to safely use prosthesis
- capable of safe but limited ambulation in her or on similar flat surface with or without AD and with or without assistance
- requires use of WC for most activities outside of residence
describe K level 2
ability or potential for ambulation with ability to transverse low level environmental barriers such as curbs, stairs, or uneven surfaces
typically limited to community ambulatory
individual can with or without AD and/or with/without assistance
- perform Level 1 tasks
- ambulate on flat/smooth surface
- negotiate curb
- access public/private transportation
- negotiate 1-2 stairs
- negotiate ramp built to ADA specs
may require WC for distances beyond perimeters of yard/driveway, apartment, etc
only able to increase their generally observed speed of walking for short distances or with great effort
describe K level 3
ability or potential for ambulation with variable cadence, typical of community ambulatory who has the ability to transverse most environmental barriers and may have vocational, therapeutic, or exercise activity that demands prosthetic utilization beyond simple locomotion
with or without assistance/AD pt can:
- walk on various textures/level
- negotiate 3-7 consecutive stairs
- walk up/down ramps
- open/close doors
- ambulate through crowded area
- cross controlled intersection within their community within the time limit provided
- access public or private transport
- perform dual ambulation tasks
describe K level 4
ability or potential for prosthetic ambulation that exceeds basic ambulation skills, exhibiting high impact stress or energy levels typical of prosthetic demands of the child, active adult, or athlete
with or without AD/assistance they can:
- run
- repetitive stair climb
- climb steep hills
- be a caregiver for another person
- home maintenance
K1 prosthetic components at the foot/ankle and the knee
foot/ankle = external keel, SACH or single axis
knee = mechanical knee with constant friction
K2 prosthetic components for foot/ankle and knee
foot/ankle = flexible keel feet, multi axial feet
knee = mechanical knee with constant friction OR mechanical knee with variable friction (hydraulic or pneumatic) OR microprocessor
K3 prosthetic components for foot/ankle and knee
foot/ankle = flex foot, energy storing feet, multi axial or dynamic response feet
knee = mechanical knee with variable friction (hydraulic or pneumatic) OR microprocessor
K4 prosthetic components for foot/ankle and knee
foot/ankle = any, includes microprocessor
knee = any
what outcome measure can be used to predict K levels
AMPPRO
describe reimbursement for prosthetic devices
every 3-5 years depending on insurance
maintenance to current device allowed
manufacturer warrantees
2 ways to fabricate a socket
casting- more traditional
scan
more pressure sensitive areas of residual limb with TTA
fibular head
end of fibula
shin bone
hamstring tendon (back)
more pressure sensitive areas of residual limb with TFA/KD
greater trochanter
ASIS
pubic tubercle
adductor tendon
IT
pubic ramus
distal femur
what is a patellar tendon bearing socket
indentation over the patellar tendon
specific pressure points
describe total surface bearing socket
distributed weight bearing
describe a quadrilateral socket for TFA
horizontal posterior self for ischial tuberosity and glutes
medial brim same as posterior shelf
anterior and lateral brims 2 1/2 - 3 inches higher
describe an ischial containment socket for TFA
medial lateral walls are more narrow
anterior wall lower
can encroach on pelvic alignment resulting in APT
describe a subischial containment socket
not as common
“brimless”
soft tissue must be able to tolerate WBing
less APT
what must a socket provide for a hip diarticulaiton or hemipelvectomy
adequate coronal support
sagittal capture of pelvic movements
secure comfortable suspension
appropriate weight bearing surfaces and contours
socket will typically encompass affected relics, gluteal tissues, and ITs
medial lateral stability provided by compression of the contralateral pelvis
socket suspension for hip disarticulation and hemipelvectomy
use of pelvic band
trim lines above iliac crest
suction or vacuum suspension
describe thigh corset suspension system
heavier and may facilitate poisoning
difficult to don
describe pin system suspension system
shuttle lock system
helps with poisoning
commonly used
describe the suction suspension systems
use a 1 way valve
pistoning can occur
will use liner, can add sock ply as needed for volume fluctuations
COMMON
describe a true suction suspension
use a 1 way valve
socket fit must be very snug
worn without a liner
benefits of a vacuum assisted sock suspension system
promote fluid exchange
reduce moisture build up
regulate volume fluctuations
increase proprioceptive awareness of limb
helps control pistoning
may help with wound healing
*expensive, heavier, and can be noisy
what is osseointegration
option for pts who do not tolerate traditional prosthetic sockets
common complications = infection and soft tissue irritation at stoma
2020 - FDA approved OPRA implant system for TFA
timeline for osseointegration
1st sx = fixture implant
bone healing x 6 months
2nd sx = abutment placed
partial WBing x 6 months
Rehab
suspension aid examples
supracondylar trim lines
outer sleeve
thigh corset
other strapping mechanisms
types of non-articulating feet
SACH feet (solid ankle cushioned heel)
types of articulating feet
single axis
multi axis
dynamic response/energy storing feet
multi axial dynamic response feet
hydraulic
microprocessor
describe the SACH foot
lightweight
inexpensive
low maintenance
wooden or metal keel that extends to MTP joints
rubber heel allows for shock absorption and PF at loading response
describe a single axis foot
some sagittal motion allowed and controlled by interchangeable anterior and posterior bumpers
no transverse or frontal plane mvmt
no energy return
heavier
More maintenance required than SACH
describe multi axial feet
allows for some pronation and supination (inversion and eversion) to cope with uneven terrain along with sagittal DF/PF
more expensive
can be heavier
for people who function in areas with uneven terrain, active amputees, golfers, and dancers
describe energy storage/dynamic response foot
leaf spring (metal or nylon) keel stores energy during 2nd rocker and releases it in the 3rd rocker
as cadence or activity level increases, more spring comes into play resulting in greater return
describe multi acial dynamic response feet
combo of articulated foot and dynamic response
closest to the functional foot replacement
describe hydraulic feet
multiaxial with vertical shock absorption
energy return
expensive, not as durable
smooth rollover
describe microprocessor/power feet
identifies slopes and stairs after first step
during gait, automatically provides DF during swing phase that allows sufficient ground clearance
active ankle motion also allows users to tuck both feet behind their knees when getting up from a chair or sitting down
automatically PFs the foot for more natural appearance when seated
advantages of microprocessor feet
provides push off
increased self selected gait velocity
9.9% less energy expenditure
disadvantages for microprocessor feet
poor battery life
heavy
expensive
types of alignment to look at for prosthetics
“bench” alignment
static = sitting/standing
dynamic = gait, STS, and stairs/ramps
things to look at with static standing alignment assessment
equal weight distribution?
level pelvis? ASIS, IC, PSIS?
foot in plantigrade?
knee position?
position of pylon?
pain?
alignment parameters to look at
- leg length
- heel height
- transverse plane foot RT
- socket sagittal plane alignment
- foot AP alignment
- socket frontal plane alignment
- foot ML alignment
- DF/PF
why do some prosthetics have adjustable heel height
to accommodate different styles of shoes
how is the prosthetic generally placed in transverse plane RT
typically mimics anatomical normal of 5-7 deg of toe out
why might a socket be placed in flexion and how does this affect the alignment
may be to accomodate knee flexion contracture
dampens shock and smooths COM rise and fall
will prevent genurecurvatum
helps resist tendency of residual limb to slide into socket and potentially bottom out
no change in sagittal plane moments
why might a socket be placed in extension and how does this affect the alignment
to attempt to correct knee flexion contracture
peak knee flexion moments increased
peak knee extension moments decreased
anterior and posterior translation of the socket has what effect on the prosthetic foot
anterior socket translation = posterior translation of foot
posterior socket translation = anterior translation of foot
what happens with socket adduction
foot must be laterally displaced
increased knee valves moment
mimics medial translation of the socket
what happens with socket abduction
foot must be medially displaced
increased knee varus moment
mimics lateral translation of socket
what happens with the foot of the prosthetic is placed lateral to the socket (socket medial to foot)
widens BOS
increased knee valgus moment
what happens when the foot of the prosthetic is placed medial to the socket (socket lateral to the foot)
maintains fairly normal BOS and loads more pressure on medial residual limb
decreases pressure on fibular head
increases knee varus moment
types of prosthetic knees
single axis hinge
ploy centric linkage
constant friction
variable friction
pneumatic
hydraulic
microprocessor
describe single axis knee joint
simple hinge mechanism
light weight
K level 1
describe polycentric knee joint
have 4 or more pivoting bars
provide greater knee stability than single axis
describe constant friction mechanism
amount of friction doesn’t change
for set cadence/walking speed
K1/K2
describe variable friction mechanism
friction changes during swing
- initial swing = high friction to prevent excess knee flexion
- midswing = friction decreases to allow knee to swing easily
- terminal swing = increase in friction to prepare for IC.
K3/K4
describe pneumatic (air) friction control system at the knee
compresses air as knee is flexed, stores energy, then energy is retuned to put knee into ext
describe hydraulic (fluid) friction control system
provide more friction and smoother gait
heavier, more expensive, require more maintenance
use a liquid medium such as silicone
describe microprocessor knees
K2-K4
sensors detect movement and timing then adjusts pneumatic or hydraulic control as needed
benefits = decreased falls, more active, enhanced confidence
heavier, expensive, need battery
why might a TFA socket be placed in flexion and what is the effect
to accomodate hip flexor contracture
weight line (TKA line) shifts posterior to the knee joint center = increased knee flexion moment
describe the control mechanisms for knee stability
alignment of knee joint axis in the sagittal plane
inherent mechanical stability of knee
voluntary control swing muscular power
microprocessor controlled
key components of prosthetic training for a pt with bilateral TFA
- build confidence- work on strength, endurance, weight management, and psychological stress
- start with short prosthetic limbs “stubbies” w/o knee joint
- COM lower to ground
- reduce fall risk
- less energy expenditure
- help improve strength - gradually increase prosthetic height
- pt will progress to full length/long prosthetic limbs with knee component
commonly observed step length/single leg stance time asymmetries
stance time = prosthetic < intact
step length = prosthetic > intact
if short step is observed on prosthetic side, possible cause = knee flexion contracture
factors that contribute to step length/single leg stance time asymmetries in pts with prosthetic limbs
pt confidence
pain
proper weight shifting
needs gait training
causes of contralateral vaulting deviation
residual limb discomfort
fear of stubbing toe
short residual limb
painful hip/residual limb
causes of hip hike deviation
weakness of hip flexors
difficulty initiating knee flexion
causes of circumduction deviation
abduction contracture
poor knee control - inability to initiate knee flexion
weakness of hip flexors
lack of confidence/training to flex knee
painful anterior distal residual limb
prosthetic causes of swing phase deviations (i.e. contralateral vaulting, hip hike, circumduction)
long prosthesis
locked knee
inadequate suspension
loose socket
foot plantar flexed
functional significance of swing phase deviations
assist with foot clearance
increases energy expenditure due to displacement of COM
prosthetic causes of ipspilateral trunk lean during prosthetic limb stance
prosthetic length too short
sharp or high medial wall (TFA/KD)
prosthetic aligned in abduction (TFA/KD)
anatomical causes of ipsilateral trunk lean during prosthetic limb stance
poor gait training
inadequate loading of prosthesis
abduction contracture
weak abductors
hip pain
instability
short residual limb
lack of proprioception
poor balance
hypersensitive or painful residual limb
