Transfemoral Prosthetics Flashcards
What is the preferred length of the femur in a transfemoral amputation?
4 inches above the knee
What types of contractures are most common in transfemoral amputees?
hip flexion and abduction
What are 3 strategies used in transfemoral amputations to reduce edema?
- IPOP
- ACE wrap
- AK shrinkers
What is essential when designing the preparatory prosthesis?
Ensure the are using the type of knee they will use forever so they can get used to it
Are end pads common in AK transfemoral prosthetics? Explain why or why not…
No, because there is increased musculature in the residual limb
What is the biggest problem with AK amputations? Because of this the main goal is to keep a(n) _____ moment during gait
keeping the knee from buckling
extension
What type of foot is preferred in a transfemoral prosthetic? Why?
SACH or single axis foot, because the foot comes down quickly in these types
How long is the preparatory stage with a AK amputation?
4-6 months
What percentage of transfemoral prosthetics are endoskeletal?
99%
What are the advantages of an endoskeletal prosthesis?
- cosmesis
- lightweight
- increased component selection
What are the disadvantages of an endoskeletal prosthesis?
- foam cover is not very durable
- increased cost
What are the advantages of an exoskeletal prosthesis?
- durable
- not very expension
What are the disadvantages of an exooskeletal prosthesis?
- heavy
- limited component selection
- not cosmetically appealing
What are 3 socket designs? What 2 are the most common?
- quadrilateral*
- ischial containment*
- plug fit-open end
What problems arise with a plug fit-open end socket?
The distal end of the residual limb does not get venous return due to the opening in the prosthesis which results in soft tissue issues
Describe the anterior and posterior dimensions of the quadrilateral socket
- flat posterior shelf which is the primary weight bearing surface for the ischium and gluteal muscles
- anterior wall contours create a posterior-directed force at the anatomical Scarpa’s triangle (holds the ischium on prosthetic seat)
The quadrilateral socket is ____ in its AP dimension than its ML dimension
narrower
Describe the concept behind the ischial containment socket
The inner (medial) wall of the socket actually cups inside the ischium, which prevents the socket from shifting laterally during the stance phase of gait
The ischial containment socket is ____ in its AP dimension than its ML dimension
wider
What are the 4 types of suspension systems that can be used in a AK amputation?
- TES belt
- Silesian bandage
- hip joint, pelvic belt, pelvic band
- suction
What does TES stand for?
Total Elastic Suspension
What is a disadvantage of the Silesian bandage?
it tends to IR the prosthesis
When are hip joint, pelvic band, pelvic belt suspension systems used?
Only when we have to, typically in amputees with short residual limbs
What is essential in order to use suction suspension?
constant residual limb volume
What are 3 types of suction liners?
- pin system
- lanyard
- seal-in liner
What is a disadvantage to the pin system?
It tends to rotate
What is an advantage of the lanyard system?
It does not allow for much rotation
What is an disadvantage of the lanyard system?
it does not allow for stair descent
Describe how seal-in liners work to suspend the prosthetic limb
It contains a hypobaric ring that when wetted with hand sanitizer it is able to slide into the socket, but once it dries it locks it in.
What is a disadvantage to the seal-in liner?
You cannot add socks to the distal end
Socket liners can be either hard or soft, what is the advantage of the soft liners?
They are soft on the pubic ramus
In transfemoral prosthetics a ____ heeled foot should be used. Why?
soft
it allows the ground reaction force to get ahead of the knee as quickly as possible
What are the 7 different kinds of prosthetic knees?
- single axis
- manual locking
- weight activated stance control (“safety knee”)
- polycentric
- pneumatic
- hydraulic
- microprocessor
What is the advantage of using the weight activated stance control knee over the single axis knee?
When there is weight being beared through the knee it is in “stance control” (it is locked) and once the knee is unloaded during swing phase it unlocks.
The single axis has no built in stability mechanism.
True or False
The stance control knee can be used for variable cadences?
False
fixed cadence only
How does the position of the multiple hinge axes on the polycentric knee play a role in stability?
Where the hinge axes intersect is where the ground reaction force is and the more anterior the GRF, the more likely the knee wants to extend (which is what we want in a AK amputation)
Does a pneumatic knee allow for variable or fixed cadence?
variable
What is the most commonly used hydraulic prosthetic knee?
Otto Bock C-Leg
What was the original hydraulic prosthetic knee?
Mauch SNS
How does the C-leg (computer leg) work?
Sensors in the pylon tell the computer what phase of gait the limb is in which then controls the hydraulic function
The C-leg processes information __ times per second
50
What are the 3 sources on input in the C-leg?
- ankle stress gauge
- knee angle position
- knee motion
What does the C-leg allow for the other prosthetic knees do not?
To climb and descend stairs reciprocally
What is the most common place for a sore to develop on the transfemoral amputee?
lateral-distal femur
What are 6 possible things that could cause a sore on the lateral-distal aspect of the femur?
- not enough socks
- AP dimension is too wide
- foot placed too far inset
- to much adduction in the socket
- poor ML stability in the socket
- not enough relief in the socket
What are the most common components of a transfemoral prosthetic?
- foot: SACH or single axis
- endoskeletal pylon
- safety knee
- ischial containment or quadrilateral socket
- any type of suspension basically
What is the main difference between transtibial and transfemoral prosthetics?
Transfemoral: maintain knee extension throughout the stance phase
Transtibial: maintain knee flexion throughout the stance phase
What is an important component of socket design that accomplishes ML femoral stabilization in a transfemoral prosthetic?
contour of the lateral wall to distribute the pressure and stabilize the femur
In the quadrilateral socket is the anterior or posterior wall higher? Which wall is the highest?
anterior
medial
In a quadrilateral socket what will occur if the AP dimension is too wide?
the ischial tuberosity will fall off of its “shelf” and the limb will fall in too far causing problems
The anterior shelf of the quadrilateral socket needs to be at least __ inch(es) higher than the posterior shelf
1
Describe why the creater of the ischial containment socket chose to narrow the ML dimension?
This does not allow for adduction of the prosthetic
The ischial containment socket uses the ______ as a block to counter the femur
ischium
Describe the dimensions of the ischial containment socket
Wide AP
Narrow ML
“tear drop”
Other than socket design socket _____ is important to accomplish ML femoral stabilization
alignment
Should the foot be inset or outset? Why?
Outset, because it reduces the varus tendancy
What are 3 things to keep the knee from buckling?
1) the alignment
2) the type of components (knee and foot)
3) the patient
What is the TKA line?
Trochanter Knee Ankle
Stationary line to identify the relative alignment between the center of the socket weight line, the rotation point of the knee and the functional rotation point of the ankle
In order to increase stability the TKA line must fall ____ of the knee
ahead
Describe what should happen if the patient has a hip flexion contracture
The socket should be flexed and moved anteriorly, or else there will be a flexion moment
_ degrees of socket flexion are required to allow for normal stride length
5
If a patient has a hip contracture what is their compensatory mechanism?
increase their lumbar lordosis
What is the landmark used when measuring transfemoral socket depth?
ischial tuberosity
In summary what does the TKA alignment do?
promotes knee stability
In summary what does socket flexion do?
allows for even stride length on the sound side
In the stance phase the foot and knee axes should be aligned in how many degrees of ER?
5-7
