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Prosthetics > TFA > Flashcards

TFA Flashcards

1
Q

bench alignment of the TFA (posterior view - frontal plane)

A

center of heel should fall just under teh ponit of contact of the ischial tuberosity with the socket

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2
Q

what is the TKA line?

A

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

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3
Q

what degree of ER does a prosthetic typically have?

A

5 degrees

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4
Q

why is the anterior wall of a TFA prosthesis about 2.5 inches taler than the posterior wall?

A

helps to keep the ischium on the shelf

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5
Q

what alignment of the prosthetic helps to generate more hip ext via glue max/hamstrings?

A

the socket is flexed about 5 degrees

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6
Q

how much should the prosthetic be adducted in a TFA?

A

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)

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7
Q

how much nrg is expended in TFA v TTA?

A

2-3x TTA nrg expenditure

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8
Q

what ms do pts use to compensate for lack of quads/knee ext?

A

GLUTES

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9
Q

likelihood of falls in TFA v TTA?

A

2x more likely w TFA

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10
Q

what % of femur length makes hip significantly weaker?

A

<57% of femur

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11
Q

“long” limb length =

A

> 60% femur length

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12
Q

to fit a standard knee unit, need — cm above knee

A

10 cm above knee

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13
Q

where does the glut max insert? what are the implications of that?

A

glut max inserts on the ITB, if ITB not reattached then you have incr hip ext weakness

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14
Q

what is the #1 priority when choosing a foot/ankle assembly for a TFA?

A

providing knee stability (usually have more adv disease, incr nrg expenditure. etc)

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15
Q

Non - articulating foot/ankle assemblies usually used

A

SACH/ Seattle Lite foot

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16
Q

which do TFAs choose normally – NES or ES?

A

NES (SACH) because most TFAs are advanced disease/elderly – exception is athletes

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17
Q

foot ankle preferences – articulating v NAR?

A

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&raquo_space; multi

  • fewer DoF
  • less instability
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18
Q

what is the “knee block”

A

thigh tube & shank connectors; contains the knee joint axis

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19
Q

what are the two main ms at risk of contracture s/p TFA?

A

ITB (hip abd) & iliopsoas (hip flex)

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20
Q

what is most difficult about stairs for TFA prostheses users/

A

descending stairs onto SOUND leg is most difficult secondary to limited knee flexion of prosthetic knee

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21
Q

why would you get a single axis v polycentric knee?

A

common/cheap, simple, low maintenance

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22
Q

for knee disarticulations, what type of knee axis should you get?

A

polycentric knee axis

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23
Q

how do spring loaded-locks in locking knees engage?

A

engage with knee ext

TOTAL stability/safety

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24
Q

what type of patient would be a good candidate for LOCKING KNEES?

A

household ambulators; severely weak, low functioning

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25
Q

how does the TFA alignment help w stance control? (single axis knee)

A

GRF anterior to knee – min req ms activity, stabilizes ankle

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26
Q

what reduces the knee flexion moment after midstance? (aka not the GRF anterior to knee)

A

longer toe lever

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27
Q

where does teh CoG fall on a polycentric knee during stance phase for stability?

A

just anterior to the posterior axis

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28
Q

what is teh PRIMARY ms to actively contribute to knee stability when using a transfemoral prosthesis?

A

glut max (secondary – hamstrings, adductor magnus, QL, paraspinals)

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29
Q

types of resistance mechanisms (4)

A
  1. mechanical (contrant v wt act)
  2. pneumatic or hydraulic
  3. microprocessor modified
  4. actuators
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30
Q

what is the safest resistance mechanism (esp for geriatrics/weak/first time users)

A

weight activiated

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31
Q

what is the lowest maintenance/cost resistance mechanism?

A

contant friction (BUT knee buckling, asc/desc stairs w step to pattern)

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32
Q

what resistance system do athletes typically prefer?

A

hydraulic (or pneumatic) == can change speeds

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33
Q

what resistance mechanism has the smoothest transfers

A

microprocessor modified

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34
Q

how would you sit down with a constance friction knee?

A

unweight leg or shift weight posterior to knee joint & the knee will flex when sitting down (no resistance to knee flexion)

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35
Q

how does a weight activated friction unit work?

A

with WBing, friction resists flexion from 0-20 BUT NO RESISTANCE after 20 (stairs = step to pattern)

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36
Q

how do you descend stairs with a hydraulic/pneumatic resistance mechanism?

A

w WBing, friction resists flexion from 0-20 BUT resistance slowly decr after 20 allowing for NORMAL STAIR DESCENT pattern

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37
Q

how do you sit down with hydraulic/pneumatic knee?

A

maintain wt on leg
reach buttock back – wait for knee to flex
resistance to flexion will shut off past ~30 deg

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38
Q

what Medicare levels can use microprocessor knees?

A

Medicare K 3-4 levels ONLY (community walkers & occasional joggers like it, but not for runners because resistance never turns off)

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39
Q

how do you SIT with a microprocessor knee?

A

ride the socket down

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40
Q

when does a microprocessor knee resist motion?

A

throughout the entire range

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41
Q

what type of patient would benefit from a power knee?

A

high functioning
on variable terrain
low/mod impact

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42
Q

IF a pt has weak hip flexors and takes very small steps, a good option for them would be..

A

a KNEE EXT AID
- could be ext (kick strap)
OR internal (wt activated, pneumatic/hydraulic, spring & cable)

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43
Q

what materials are used with an inner socket? which one can expand with ms contraxn?

A

polyethylene or pelite liner

- polyethylene can expand w ms contraxn

44
Q

which socket design gives relief for the adductor tendon? where do you weight bear?

A

the quadrilateral design

WBing thru ischial tub on posterior ledge

45
Q

what are the 3 bony points of control of an ischial containment socket?

A
  1. ischial ramus 2. ischial tuberosity 3. greater troch
46
Q

what are 2 socket modifications that can be done to allow for some ms hypertrophy?

A

lower AP trim lines, compression/release design (bigger fenestrations)

47
Q

what type of patient is partial suctioning used for?

A

first time user, immature limb, must have dexterity still (also req auxillary suspension - less secure v total suction)

48
Q

req for a full suction suspension system?

A

stable volume, mature, well shaped, strong limb;
active individuals
req more skill/strength/balance to don
– offers VERY secure suspension w more sensory feedback

49
Q

why would you use a shoulder harness auxillary suspension system? (4 pts)

A
  1. pt obesity
  2. scar tissue
  3. excessively short limb
  4. colostomy bag
50
Q

a pelvic belt auxillary suspension is good if..

A

pt has no preosthetic support, but HEAVY design w/o rotary or M/L motion

51
Q

Silesian bandage advantages:

A

more mobility v pelvic band, added stability for short, weak or flabby limbs , simple and cheap

52
Q

neoprene sleeve is more comfortable and is very secure – what patients is it indicated for?

A

young, more mobile patients (req stronger limb)

53
Q

silicone suction suspension requires what kind of limb?

A

long, mature, stable volume ; BUT costly, complex

54
Q

what kind of sleeve does a vacuum assisted suspension system use?

A

silicone

55
Q

how would you don a prosthetic for a hip disarticulation?

A

wrap around

56
Q

the pull thru TF donning method is for — suctioning.

A

partial or full suctioning

57
Q

for skin and seal-in suction socket systems, use teh — donning method

A

wet-fit TF donning –

  • cover entire limb w lotion to decr friction
  • quick simple cheap, more secure
58
Q

where do you check for total contact?

A

at the valve hole (initially with a check socket)

59
Q

what areas should you build up a tolerance to pressure (as opposed to relieving it)? (2)

A
  1. lateral thigh

2. soft tissues of the posterior thigh & buttock

60
Q

position of the femur relative to teh hip in sagittal plane =

A

slightly flexed (socket flexed 5-10 deg)

61
Q

when the socket is adducted 7-10 dg, this places the foot.. and where does the majority of the WBing take place?

A

foot under pelvis for normal BoS

Incr lat thigh WBing (ITB is very P tolerant)

62
Q

where should the ML weight line fall for a TFA?

A

1 cm inset

  • may avoid thrust
  • puts HIP ABDS at a MECH ADVANTAGE
  • FACILITATES GLUT MED by putting it on stretch
  • incr gait efficiency
63
Q

should the foot be inset or outset?

A

INSET foot decreases medial moment at foot , outset foot incr stance instability

64
Q

transverse plane alignment of foot =

A

5-10 deg toe out

65
Q

if the pt can’t lean fwd w/o discomfort, most likely the …

A

anterior brim is too high causing incr P on femoral triangle

66
Q

how do you check to see if “redundant tissue” is contained in the prosthesis of a TFA?

A

look for adductor roll == could indicate incorrect donning or that socket is too small

67
Q

if you have a B amputee (1 TFA & 1 TTA), which side should be shorter? why?

A

TFA because TTA can bend knee more in stance

68
Q

leg lengths should be within — cm of each other

A

1 cm

69
Q

if the knee is too stable/ stiff in ext, problem could be that the foot is..

A

in too much PF

70
Q

3 indications that suspension is not maintained during gait?

A
  1. excessive pistoning ( air escaping)
  2. ” “ lateral gapping (>2 fingers)
  3. toe drag
71
Q

3 common sounds a prothetic SHOULD be making

A
  1. bumper impacting in ankle PF or knee ext
  2. ankle or knee jt noise
  3. suction sucking sounds
72
Q

if during gait the ipsi UE stays ext, indicative of..

A

ipsi short limb

73
Q

if during gait the ipsilat limb is circumducting/hiking, indicative of..

A

ipsilateral limb too short

74
Q

if during swing you notice a medial whip with hip ER, indicative of a ..

A

shortened ipsilat limb

75
Q

if in midstance you see a narrow BoS & lateral thrust, indicative of ..

A

ipsilateral limb shortened

76
Q

excessive trunk extension in midstance is indicative of.. (ipsi long or short? )

A

ipsi LONG

77
Q

pt causes of knee buckling at IC & Loading –

A

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

78
Q

excessive trunk ext : pt causes?

A
  1. weak gluts (paraspinals compensating)
  2. lmtd hip ext ROM
  3. weak abdominals/ spinal instability
    PROSTHETIC cause : insufficient socket flexion
79
Q

3 patient causes of lateral trunk lean in midst?

A
  1. weak glut med
  2. hip abductor contracture
  3. poor WB acceptance/habit
    PROSTHETIC == anything causing a medial moment liek foot outset; prosthesis too short/ medial brim too high
80
Q

what type of gait deviance could be indicative of pain at perineum? (sacral ulcer also..)

A

medial thrust (wide BoS)

81
Q

excessive socket flexion could cause — at the pelvis during MidSt?

A

pelvic retraction (also could be due to insuff ankle DF,/long toe lever)

82
Q

what kind of toe lever would promote early heel rise?

A

shortened toe lever

83
Q

if using a wt activated resistance mechanism and pt experiences early heel rise, most likely..

A

inadequately WBing

84
Q

lateral whip (hip IR) would indicate tight…

A

ITB/TFL, hip adductors; weak hip ER

85
Q

what ms normally decelerates tibia at terminal ext?

A

hamstrings

86
Q

for a B/L TFA, what should be used for stability with prolonged standing?

A

locking knee

87
Q

for a B TFA what type of knee should be used for safe function? how about if lower level but need safety?

A

polycentric knee; wt activated knee w ext aid for safety

88
Q

leading cuase of death of B TFA

A

MI (mean life expectancy >4 yrs

89
Q

TFA v TTA length

A

TFA should be 1 cm shorter

90
Q

most of strength for B TFA pts comes from..

A

trunk

91
Q

main focus of ms strengthening s/p TMT (tarsometatarsal) amputation

A

hip strengthening!

92
Q

what type of orthosis should a TMA have?

A

rocker sole (decr pressure),
molded foot plate & attached toe filler
OR stiff insole/board lasted shoe

93
Q

orthotic for TMT amputee?

A

PLO w toe resilient filler

94
Q

with hip disarticulation, WBing thru..

A

ischial tuberosity & gluteal flaps

95
Q

w hemipelvectomy, WB thru..

A

compressed abdominal contents

96
Q

what type of knee do hip disarticulation pts usually opt for? what about foot/ankle assembly?

A

constant friction knee set in hyperext

SACH foot NAR NES OR single axis (better knee stability)

97
Q

with a hip disarticulation, how is the knee stable past midsts?

A

secondary to alignment

98
Q

4 early goals in amputee gait training

A
  1. wt shifting
  2. load acceptance
  3. balance
  4. knee control
99
Q

with a MPK, you should initiate swing with..

A

forefoot WBing

100
Q

with a HYDRAULIC knee, initiate swing phase with..

A

knee ext

101
Q

witha POLYCENTRIC knee, initiate swing phase w ..

A

anterior elevation

102
Q

how do friction knee users ascent/descend stairs?

A

step to pattern, NORMAL up w good down w bad

103
Q

what is more difficult for a HYDRAULIC knee user – ascent or descent of stairs?

A

ascent because no resistance to knee flexion (same with MKP – no power up!)
*must descend with toe off step

104
Q

w a prosthetic, where should the weight be to maintain knee ext w turning

A

on prosthetic toe

105
Q

knee ext is how much weaker in prosthetic v intact limb

A

up to 50% – quads more atrophied than hammies

106
Q

with ACTIVE TTA users, their TTA hips are — compared to intact hip

A

11-14% STRONGER

Prosthetics (4 decks)

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