biomechanics Flashcards
BK
Total Contact (3)
P= F/A
we want as much residual limb in contact as possible
1-better venous return if total contact
2-dont want distal edema to accumulate
3-it will feel less heavy if there is no gapping
BK
Anteriorly Tilt Socket (3)
“flexing the socket” (~5 degrees): get the knee into a more flexed attitude
- improves WB to tolerant areas: WB infrapatella tendon, less distal stump
- Promotes Knee Flexion in EARLY STANCE: HS knee extended and then 15-20 degrees flexed at FF
- accommodates for knee flexion contracture
If patient BK has a flexed knee contracture, what to do to adjust the socket
anterior tilt the socket further to acomodate to the contracture = flexing the socket
BK anterior tilt socket
- improves WB to tolerant areas:
- Promotes Knee Flexion in EARLY STANCE:
- accommodates for knee flexion contracture
- infrapatella tendon, less on distal stump
- HS knee extended and then 15-20 degrees flexed at FF
- accommodates for knee flexion contracture
BK
ankle foot slightly posterior
ankle foot set slightly posterior in relation to the center of the socket
- promotes knee flexion in EARLY STANCE
- set heel 1/4 inch slightly posterior
BK
ankle foot set slightly medial
- increases varus moment
- improves pressure distribution to proximal medial / distal lateral residual limb
- -not at fibular head
BK
what to do if too much pressure proximal and medial
move the ankle foot closer to the center of socket
BK
what promotes knee flexion in early stance?
- anteriorly tilt socket “flexed socket”
2. ankle set slightly posteriorly
BK
What improves pressure distribution?
ankle foot slightly posterior
BK what accomodates for knee flexion contracture?
BK anterior tilt socket
BK
What increases Varus moment?
ankle foot set slightly medial
BK
what improves pressure distribution to proximal medial / distal lateral residual limb
ankle foot set slightly medial
BK
what improves WB to tolerant areas: WB infrapatella tendon, less distal stump
Anteriorly Tilt Socket
AK
Posterior Tilted Socket
“flexing the socket”
- accommodates for tight hip flexors
- maintain a better length tension on extensors: lengthen the extensors for more force generation in STANCE
- help activate the shank/foot position in LATE STANCE: with less need hip extension
- improve WB tolerance on Ischial Shelf
AK
Adduct Lateral Wall
prevent residual limb from going into abduction (for the gluteus medius to be in a good position)
AK
TKA line and knee stability
ankle axis posterior to create greater extension moment
AK
what accommodates tight hip flexors?
AK posterior tilted socket
AK
what to do for a hip flexion contracture?
AK posterior tilt socket
AK
what to maintain better length tension on extensors?
AK posterior tilt socket
better length tension on extensors , lengthens the extensors for more force generation in the STANCE phase
AK
what to activate the shank / foot position in late stance
AK posterior tilt socket
in late stance the lower leg and foot is back, tilt the socket back to go further back
dont need to do as much hip extension in LATE STANCE to get the prosthesis into a more extended position
need hip extension to get foot back, posterior tilt socket so as come to midstance and heel rise and the hip comes back the lower portion of the prosthesis gets back into terminal stance position
AK
what improves WB on ischial shelf?
AK posterior tilt socket
more comfortable instead of sitting straight on shelf
come in at an angle to decrease torque / force around the IT and overlying tissue
AK
what prevents residual limb from going into abduction?
AK
adduction of the lateral wall (about 10 degrees)
–for mechanical advantage of gluteus medius
TKA line and knee stability
ankle axis is posterior to create a greater extension moment
TROCHANTERIC ANKLE LINE
-center of socket to center of ankle/foot assembly
knee unit is slightly posterior 1/4 inch
for weight line to be further in front to increase extension stability in knee by putting weight in front of the knee (bc axis is further back)
AK
what increases extension stability?
TROCHANTERIC ANKLE LINE
-center of socket to center of ankle/foot assembly
knee unit is slightly posterior 1/4 inch
for weight line to be further in front to increase extension stability in knee by putting weight in front of the knee (bc axis is further back)
