TFA socket and alignment Flashcards
objective of all prosthetic sockets is what three things?
Provide stability
Maintain suspension
Interface with the residual limb
Knee disarticulation what is the benefit?
the femoral condyles act as a wt. bearing surface that is meant to be wt. bearing in the body!
Quad socket is narrow in what dimension?
AP
ischial wt. bearing shelf is what socket
quad
What kind of contact does the quad socket have?
total contact: there are areas of wt. relief and built up areas based on pressure sensitive and tolerant areas
height of the medial wall in quad socket? (2 things to think about)
equal posterior wall
contains the ADD tissue
How the the posterior wall slope in a quad socket? Why?
Slopes anteriorly to provide a surface for the hip extensors to push on in order to control the knee
Where does the lateral wall of the quad socket extend to?
the greater trochanter
What is the highest wall of the quad socket
lateral wall, goes up to greater trochanter
What degrees of ABD or ADD is the lateral wall of the quad socket in? why?
10 degrees of ADD to put the ABD at a mechanical advantage
Anterior wall of quad socket in comparison to posterior wall
2 inches higher
Where is there pressure anteriorly in a quad socket?
scarpas bulge: femoral triangle to push pt onto ischia seat and prevent rotation of the socket
Scarpas bulge pushes on what? for what purpose?
femoral triangle to push pt onto ischial seat and prevent rotation of socket
IC what dimension is narrow
ML
Is quad or IC better for a more active individual?
IC
Two goals of IC
contain muscle groups and create stability
Where is the butt bone in an IC socket?
the ischium is contained! The posterior wall is higher
Is the posterior wall higher in quad or IC?
IC: IT is actually inside the socket
Posterior wall sloping for IC?
same as quad socket, anterior sloping to give hip extensors something to extend against
Medial wall of IC encloses what?
public rampus
In a IC socket the medial wall provides _______ to lateral wall
counter pressure: squeezes the femur creating stability
True or false: you should be able to feel the greater trochanter in IC socket
no! the lateral wall should be above it
IC socket is 10-15 degrees of what in the frontal plane? for what purpose
10-15 degrees of ADD
This puts the TFL and lateral hamstrings on stretch leading to mechanical advantage for them
Does IC have scarpas bulge?
yes but normally its not as prominent.
What kind of patient coulds use a sub-ischial socket?
“long and strong” a very strong individual. This socket wouldn’t contain the ischium or greater troch.
In quad socket what is the purpose of the medial wall?
contain ADD tissue
What does someone have to prove to be put in a sub-ischial socket?
they are very strong in ADD tissue
Hi-Fi socket general picture
cut outs of hard material that lock into the bones, there are large areas of sot tissue relief
Silesian band attaches how
near trochanter, wraps around waist and anchors onto iliac crests
Advantages of silesian band suspension?
cheap
easy to fabricate
easy to don
Disadvantage of silesian band?
not great at its job
larger habitus won’t be able to lock onto iliac crests and therefore won’t work
One major advantage of pelvic band and external hip joint suspension?
if someone has very weak hip joint helps ABD control due to the stability it gives you
3 disadvantages of pelvic band and external hip joint suspension?
Heavy
Hard to don
Can cause rotations
Appropriate population for silesian band?
obviously iliac crests
Appropriate population for pelvic band and external hip joint suspension
really weak hip
Suspenders are used in what event/population (3 things)
last resort when silesian or pelvic band are not appropriate
not a candidate for suction
Short TFA or hemipelvectomy
TESS belts two advantages
abdominal surgery
back up suspension
TESS bests two disadvantages
minimal suspension (so used more as back up)
poor control of rotation
Population for TESS belts?
very active population for back up suspension use rather than primary
Traditional suction works by what means?
negative pressure
How do you don traditional suction?
skin goes right into the socket and then you bleed the air through the valve at distal end.
Advantages of this kind of suspension include
intimate fit
lots of degrees of motion
comfort
minimal pistoning
use of musculature to keep it on, the pt doesn’t have to use their own
Traditional suction
Disadvantages of traditional suction
hard to don
not adaptable to girth fluctuations
difference btwn partial suction and traditional and the advantage to this
prosthetic sock used
Better adaptable to changes in volume
How to don 3S
totally inside out, roll it onto the limb and then lock in with either a pin or lanyard to the socket
how to don seal in liner
moisten outer part of liner with alcohol water mixture to slide in, force air out of one way valve
What two thing are advantages to 3S suspension that traditional suction does not have?
Allows for volume fluctuation
Easy to don
Disadvantages to 3S suspension
skin reactions
care and maintenance
careful of air-pocket
improper donning
rather than sliding down into their socket what can people do
step into their socket
What is a good method to get traditional suction socket on. three ways
Pull in method w/pull sock
Stand up into it
Bleeding the air/pump
if you have a 3S liner, socket and sock, what order do you put them on
Liner against skin
Sock if necessary
Socket
What is the primary goal of prosthetic knees? Secondary/
primary: knee stability
secondary: knee mobility
in general stance phase control means what?
swing phase control?
stance phase control: controls or limits knee flexion while wt. bearing
swing phase control: limits or assists flexion or extension
Name the three methods of achieving knee stability in stance phase
1) muscular action: mostly hip extensors
2) alignment wt. line anterior to jt axis
3) mechanical device: locked friction, hyraulic cylinder
Talk about where the weight line and axis of the knee should be for stability (say it both ways)
Knee axis should be posterior to weight line
Weight line should be anterior to knee axis
Swing control is achieved through what 5 things
movement of residual limb and pelvis
gravity
momentum
Mechanical extension assist
mechanical adjustment for limiting or assisting with flexion or extension
Name the 7 categories of knee joints from most basic to most advanced
1) manual lock
2) constant friction
3) wt. activated/stance control
4) polycentric
5) gas/fluid control
6) micro-processor
7) power knee
Manual lock knee
Jt. axis:
Stance control:
Swing control:
Jt. axis: single
Stance control: max mechanical
Swing control: max mechanical
patient popultation for manual lock knee
weak pt, limited ambulator, no control of knee
How does the patient ambulate with the most basic knee
most basic knee = manual lock therefore they walk with the locked knee with abnormal gait pattern, prosthesis is shorter for clearance reasons
Constant friction knee
where out of the 7 is it?
Jt. axis:
Stance control:
Swing control:
2nd
Jt. axis: single
Stance control:
- muscular control
- alignment
Swing control:
- friction to limit flexion and extension
- extension assist possible
indications for constant friction knee
long time user resistant to change
limited access to follow up
good muscular control
disadvantages for constant friction knee
fixed cadence
unstable especially on uneven surfaces
Number 3/7 knee joint
weight activated/stance control
Number 2/7 knee joint
constant friction
Weight activated stance control
Jt. axis:
Stance control:
Swing control:
jt axis: single
Stance control:
- moderate mechanical
Swing control:
- friction
- can add extension assistance
indications for weight activated stance control
weaker pt with some inability to control the knee
Major disadvantage to wt activated stance control
knee flexion inhibited in pre-swing: they have to fully unweight it to allow it to bend
Polycentric knee
Jt. axis:
Stance control:
Swing control:
jt axis: multiple Stance control: - moderate alignment - muscular control Swing control: - extension assit or hydraulic add ons
indications for polycentric knee
knee disarticulation
Short residual limb, weak hip extensors (requiring greater stability and not a higher level knee)
But active: high K2 and K3
What is the single most important thing to take away about the polycentric knee
As the knee bends, the axis of rotations moves posteriorly and superior/proximally, just like a real knee joint.
In polycentric knee the center or rotation displacing posteriorly increases the _____ moment increasing or decreasing stability
In polycentric knee the center or rotation displacing posteriorly increases the external EXTENSION moment therefore INCREASING stability
4/7 kind of knee
polycentric
5/7 kind of knee
fluid controlled
Fluid controlled (5)
Jt. axis:
Stance control:
Swing control:
Jt. axis: single Stance control: - mechanical position of piston - muscular Swing control: - mechanical with flexion and/or extension resistance
what is the first knee of the 7 can someone run reciprocally in
fluid controlled (5)
Caveat of fluid controlled reciprocal units
cadence is not responsive, they can run but only at one speed
6/7 kind of knee
microprocessor
Microprocessor explain detecting knee motion
Cadence adjustable?
Detects knee motion via pressure and motion sensing
true adjustable cadence
Indications for microprocessor (6)
active ambulator
Variable cadence
Descent of stiars/inclines
7th kind of knee
power knee
what kind of knee(s) can you reciprocally ascend steps?
only power knee (7/7)
indications for power knee
unilateral TFA
moderate/active
low weight
what allows individuals to corss legs, change shoes, sit in car
knee rotator
what does a ferrier coupler do
easily take out knee to be able to swap feet easily
name the 4 translational changes to TFA you could make
socket inset or outset
knee and foot forward or backward
name the 8 angular changes to TFA you could make
Foot: DF, PF, Inversion, Eversion
Socket: flex, extend, ABD, ADD
name the 2 rotational changes to FA you could make
toe in or out
knee IR, ER
if you flex the TF socket what are you doing at the hip
flex the socket, flex the hip
bench alignment should always take into account what?
How?
why?
contractures
flexion plate
you cant just flex the socket because this will put the wt. line behind the axis making the knee want to buckle
normal TFA alignment in the sagittal plane
Ankle:
Socket
Weight line ____ to knee
normal TFA alignment in the sagittal plane
Ankle: neutral
Socket: flexed 5-10 degrees (allows hip extensors to be mechanically advantageous)
Weight line: ANTERIOR to knee FOR STABILITY
Normal TFA alignment in the frontal plane
Socket:
Foot: to produce _____
Socket: slight ADD so ABD are at mechanical advantage
Foot: slight inset to produce slight VARUS moment at knee during gait like normal person
what needs to be accommodated for in the angle of the socket?
hip flexion contractures
if someone has a hip flexion contracture of 7 degrees what should their socket be set in in this plane
normal (10 degrees degrees) + contracture (7 degrees) =17 degrees flexion
what should you do before gait assessment?
check if prosthesis is aligned properly
distal end pain, pain on IT’s may tell you what about the fit of the socket?
they’re in too far
what signs may tell you someone is not in their socket enough
tibial pain, IT too high, circumduction of leg
three big picture things to look at first with gait analysis
speed
pattern
midline orientation
is a new user more likely to have narrow BOS or wider?
wider for more stability
Shorter step length when
Shorter stance time when
with new prosthetic user
shorter step length on intact side
shorter stance time on involved side
likely step to
gait training the order of importance of 4 things
fit/comfort of socket
stance phase deviations
swing phase deviations/timing
symmetry
when you see deviation what are you trying to decide
patient?
device?
both?
