TFA Flashcards
bench alignment of the TFA (posterior view - frontal plane)
center of heel should fall just under teh ponit of contact of the ischial tuberosity with the socket
what is the TKA line?
in the SAGITTAL plane, the bench alignment of the TFA: trochanter-knee-ankle line; T mark= xfer’d from a point 1-in ant to the posteromedial corner of the inside of the socket
—GRFV is aligned ANTERIOR to teh knee jt, producing an EXT moment
what degree of ER does a prosthetic typically have?
5 degrees
why is the anterior wall of a TFA prosthesis about 2.5 inches taler than the posterior wall?
helps to keep the ischium on the shelf
what alignment of the prosthetic helps to generate more hip ext via glue max/hamstrings?
the socket is flexed about 5 degrees
how much should the prosthetic be adducted in a TFA?
about 7 degrees (the femur tends to become more vertical because of the imbalance of forces between teh abductors and adductors, so this positions the femur in a more anatomic plane, and maintains the length/tension ratio for the GLUT MED)
how much nrg is expended in TFA v TTA?
2-3x TTA nrg expenditure
what ms do pts use to compensate for lack of quads/knee ext?
GLUTES
likelihood of falls in TFA v TTA?
2x more likely w TFA
what % of femur length makes hip significantly weaker?
<57% of femur
“long” limb length =
> 60% femur length
to fit a standard knee unit, need — cm above knee
10 cm above knee
where does the glut max insert? what are the implications of that?
glut max inserts on the ITB, if ITB not reattached then you have incr hip ext weakness
what is the #1 priority when choosing a foot/ankle assembly for a TFA?
providing knee stability (usually have more adv disease, incr nrg expenditure. etc)
Non - articulating foot/ankle assemblies usually used
SACH/ Seattle Lite foot
which do TFAs choose normally – NES or ES?
NES (SACH) because most TFAs are advanced disease/elderly – exception is athletes
foot ankle preferences – articulating v NAR?
articulating preferred (single axis)
- more stable
- greater knee ext moment
- quickly progresses to foot flat
- accommodates for terrain/slopes
- more comfortable in gait
single axis»_space; multi
- fewer DoF
- less instability
what is the “knee block”
thigh tube & shank connectors; contains the knee joint axis
what are the two main ms at risk of contracture s/p TFA?
ITB (hip abd) & iliopsoas (hip flex)
what is most difficult about stairs for TFA prostheses users/
descending stairs onto SOUND leg is most difficult secondary to limited knee flexion of prosthetic knee
why would you get a single axis v polycentric knee?
common/cheap, simple, low maintenance
for knee disarticulations, what type of knee axis should you get?
polycentric knee axis
how do spring loaded-locks in locking knees engage?
engage with knee ext
TOTAL stability/safety
what type of patient would be a good candidate for LOCKING KNEES?
household ambulators; severely weak, low functioning
how does the TFA alignment help w stance control? (single axis knee)
GRF anterior to knee – min req ms activity, stabilizes ankle
what reduces the knee flexion moment after midstance? (aka not the GRF anterior to knee)
longer toe lever
where does teh CoG fall on a polycentric knee during stance phase for stability?
just anterior to the posterior axis
what is teh PRIMARY ms to actively contribute to knee stability when using a transfemoral prosthesis?
glut max (secondary – hamstrings, adductor magnus, QL, paraspinals)
types of resistance mechanisms (4)
- mechanical (contrant v wt act)
- pneumatic or hydraulic
- microprocessor modified
- actuators
what is the safest resistance mechanism (esp for geriatrics/weak/first time users)
weight activiated
what is the lowest maintenance/cost resistance mechanism?
contant friction (BUT knee buckling, asc/desc stairs w step to pattern)
what resistance system do athletes typically prefer?
hydraulic (or pneumatic) == can change speeds
what resistance mechanism has the smoothest transfers
microprocessor modified
how would you sit down with a constance friction knee?
unweight leg or shift weight posterior to knee joint & the knee will flex when sitting down (no resistance to knee flexion)
how does a weight activated friction unit work?
with WBing, friction resists flexion from 0-20 BUT NO RESISTANCE after 20 (stairs = step to pattern)
how do you descend stairs with a hydraulic/pneumatic resistance mechanism?
w WBing, friction resists flexion from 0-20 BUT resistance slowly decr after 20 allowing for NORMAL STAIR DESCENT pattern
how do you sit down with hydraulic/pneumatic knee?
maintain wt on leg
reach buttock back – wait for knee to flex
resistance to flexion will shut off past ~30 deg
what Medicare levels can use microprocessor knees?
Medicare K 3-4 levels ONLY (community walkers & occasional joggers like it, but not for runners because resistance never turns off)
how do you SIT with a microprocessor knee?
ride the socket down
when does a microprocessor knee resist motion?
throughout the entire range
what type of patient would benefit from a power knee?
high functioning
on variable terrain
low/mod impact
IF a pt has weak hip flexors and takes very small steps, a good option for them would be..
a KNEE EXT AID
- could be ext (kick strap)
OR internal (wt activated, pneumatic/hydraulic, spring & cable)
what materials are used with an inner socket? which one can expand with ms contraxn?
polyethylene or pelite liner
- polyethylene can expand w ms contraxn
which socket design gives relief for the adductor tendon? where do you weight bear?
the quadrilateral design
WBing thru ischial tub on posterior ledge
what are the 3 bony points of control of an ischial containment socket?
- ischial ramus 2. ischial tuberosity 3. greater troch
what are 2 socket modifications that can be done to allow for some ms hypertrophy?
lower AP trim lines, compression/release design (bigger fenestrations)
what type of patient is partial suctioning used for?
first time user, immature limb, must have dexterity still (also req auxillary suspension - less secure v total suction)
req for a full suction suspension system?
stable volume, mature, well shaped, strong limb;
active individuals
req more skill/strength/balance to don
– offers VERY secure suspension w more sensory feedback
why would you use a shoulder harness auxillary suspension system? (4 pts)
- pt obesity
- scar tissue
- excessively short limb
- colostomy bag
a pelvic belt auxillary suspension is good if..
pt has no preosthetic support, but HEAVY design w/o rotary or M/L motion
Silesian bandage advantages:
more mobility v pelvic band, added stability for short, weak or flabby limbs , simple and cheap
neoprene sleeve is more comfortable and is very secure – what patients is it indicated for?
young, more mobile patients (req stronger limb)
silicone suction suspension requires what kind of limb?
long, mature, stable volume ; BUT costly, complex
what kind of sleeve does a vacuum assisted suspension system use?
silicone
how would you don a prosthetic for a hip disarticulation?
wrap around
the pull thru TF donning method is for — suctioning.
partial or full suctioning
for skin and seal-in suction socket systems, use teh — donning method
wet-fit TF donning –
- cover entire limb w lotion to decr friction
- quick simple cheap, more secure
where do you check for total contact?
at the valve hole (initially with a check socket)
what areas should you build up a tolerance to pressure (as opposed to relieving it)? (2)
- lateral thigh
2. soft tissues of the posterior thigh & buttock
position of the femur relative to teh hip in sagittal plane =
slightly flexed (socket flexed 5-10 deg)
when the socket is adducted 7-10 dg, this places the foot.. and where does the majority of the WBing take place?
foot under pelvis for normal BoS
Incr lat thigh WBing (ITB is very P tolerant)
where should the ML weight line fall for a TFA?
1 cm inset
- may avoid thrust
- puts HIP ABDS at a MECH ADVANTAGE
- FACILITATES GLUT MED by putting it on stretch
- incr gait efficiency
should the foot be inset or outset?
INSET foot decreases medial moment at foot , outset foot incr stance instability
transverse plane alignment of foot =
5-10 deg toe out
if the pt can’t lean fwd w/o discomfort, most likely the …
anterior brim is too high causing incr P on femoral triangle
how do you check to see if “redundant tissue” is contained in the prosthesis of a TFA?
look for adductor roll == could indicate incorrect donning or that socket is too small
if you have a B amputee (1 TFA & 1 TTA), which side should be shorter? why?
TFA because TTA can bend knee more in stance
leg lengths should be within — cm of each other
1 cm
if the knee is too stable/ stiff in ext, problem could be that the foot is..
in too much PF
3 indications that suspension is not maintained during gait?
- excessive pistoning ( air escaping)
- ” “ lateral gapping (>2 fingers)
- toe drag
3 common sounds a prothetic SHOULD be making
- bumper impacting in ankle PF or knee ext
- ankle or knee jt noise
- suction sucking sounds
if during gait the ipsi UE stays ext, indicative of..
ipsi short limb
if during gait the ipsilat limb is circumducting/hiking, indicative of..
ipsilateral limb too short
if during swing you notice a medial whip with hip ER, indicative of a ..
shortened ipsilat limb
if in midstance you see a narrow BoS & lateral thrust, indicative of ..
ipsilateral limb shortened
excessive trunk extension in midstance is indicative of.. (ipsi long or short? )
ipsi LONG
pt causes of knee buckling at IC & Loading –
weak gluts, hip flex contacture, pain
- prosthetic – insufficient ankle PF , COG posterior to kneee axis, insufficient socket flexion, inadequate WBing w MPK or inadequate stance phase resistnace w hydraulic knees
excessive trunk ext : pt causes?
- weak gluts (paraspinals compensating)
- lmtd hip ext ROM
- weak abdominals/ spinal instability
PROSTHETIC cause : insufficient socket flexion
3 patient causes of lateral trunk lean in midst?
- weak glut med
- hip abductor contracture
- poor WB acceptance/habit
PROSTHETIC == anything causing a medial moment liek foot outset; prosthesis too short/ medial brim too high
what type of gait deviance could be indicative of pain at perineum? (sacral ulcer also..)
medial thrust (wide BoS)
excessive socket flexion could cause — at the pelvis during MidSt?
pelvic retraction (also could be due to insuff ankle DF,/long toe lever)
what kind of toe lever would promote early heel rise?
shortened toe lever
if using a wt activated resistance mechanism and pt experiences early heel rise, most likely..
inadequately WBing
lateral whip (hip IR) would indicate tight…
ITB/TFL, hip adductors; weak hip ER
what ms normally decelerates tibia at terminal ext?
hamstrings
for a B/L TFA, what should be used for stability with prolonged standing?
locking knee
for a B TFA what type of knee should be used for safe function? how about if lower level but need safety?
polycentric knee; wt activated knee w ext aid for safety
leading cuase of death of B TFA
MI (mean life expectancy >4 yrs
TFA v TTA length
TFA should be 1 cm shorter
most of strength for B TFA pts comes from..
trunk
main focus of ms strengthening s/p TMT (tarsometatarsal) amputation
hip strengthening!
what type of orthosis should a TMA have?
rocker sole (decr pressure),
molded foot plate & attached toe filler
OR stiff insole/board lasted shoe
orthotic for TMT amputee?
PLO w toe resilient filler
with hip disarticulation, WBing thru..
ischial tuberosity & gluteal flaps
w hemipelvectomy, WB thru..
compressed abdominal contents
what type of knee do hip disarticulation pts usually opt for? what about foot/ankle assembly?
constant friction knee set in hyperext
SACH foot NAR NES OR single axis (better knee stability)
with a hip disarticulation, how is the knee stable past midsts?
secondary to alignment
4 early goals in amputee gait training
- wt shifting
- load acceptance
- balance
- knee control
with a MPK, you should initiate swing with..
forefoot WBing
with a HYDRAULIC knee, initiate swing phase with..
knee ext
witha POLYCENTRIC knee, initiate swing phase w ..
anterior elevation
how do friction knee users ascent/descend stairs?
step to pattern, NORMAL up w good down w bad
what is more difficult for a HYDRAULIC knee user – ascent or descent of stairs?
ascent because no resistance to knee flexion (same with MKP – no power up!)
*must descend with toe off step
w a prosthetic, where should the weight be to maintain knee ext w turning
on prosthetic toe
knee ext is how much weaker in prosthetic v intact limb
up to 50% – quads more atrophied than hammies
with ACTIVE TTA users, their TTA hips are — compared to intact hip
11-14% STRONGER
