6: Transfemoral Flashcards
After a TFA, how much weight can be placed directly on the end of the residual limb?
Very little to none
How are thigh muscles balanced following a TFA?
Flexors and abductors overpower the extensors and adductors
What is the goal of TFA?
regain muscle balance and position the femur for weight bearing and ambulation
Are the primary hip flexors and hip abductors affected by TFA?
No because their attachment sites are more proximal than the amputation level
What causes adductor and extensor weakness following TFA?
Loss of distal muscle attachment sites
Where are adductor muscles secured?
To the residual femur to prevent abduction
Why is it important to prevent the femur from abducting?
Weight cannot be loaded as easily and the bone my press painfully against the socket
With surgically balanced muscles, where does the majority of weight bearing in the socket occur?
On the sides of the legs, not on the distal end
What is adduction roll?
Collection of tissue that sometimes forms high on the inner thigh above the socket line
What are common causes of adductor roll?
Weight gain, mismatched socket geometry, improper donning of residual limb
What is the minimal length for a TFA?
7.5 cm
What is the optimal length for a TFA?
23-30 cm
What are the 6 pressure sensitive areas following a TFA?
- ASIS
- Greater trochanter
- Pubic tubercle
- Adductor tendon
- Public ramus
- Distal femur
What are the five components of a prosthetic for a TFA?
Socket, rotator, knee joint, pylon, foot
What are the four types of prosthetic knees?
- Single axis hinge
- Polycentric
- Pneumatic and hydraulic
- Microprocessor
What K level is indicated for a single axis hinge?
K1 or K2
What K level is indicated for a polycentric knee?
K1 or K2
What K level is indicated for a pneumatic and hydraulic knee?
K3
What K level is indicated for a microprocessor knee?
K4
What are the two types of knee friction?
Constant or variable friction
What K level is indicated for constant friction?
K1 or K2
What K level is indicated for variable friction?
K3
Describe a knee-single axis joint
Difficult to reciprocate during gait. Can have a knee extension assist or weight-activated stance phase control. Light weight
What types of mechanisms are present in a knee-single axis joint?
Constant friction and simple hinge
Describe a polycentric joint
Heavier, reciprocal gait is more fluid, may or may not have a knee extension assist or a weight-activated stance phase control. Have four or more pivoting bars
Which provides greater stability, polycentric or single axis joints?
Polycentric
Describe a constance friction mechanism
Amount of friction does not change with a set cadence and walking speed
What type of knee joints have constant friction mechanisms?
Single-axis and polycentric
What K levels are indicated for a constant friction mechanism?
K 1 and 2
What K levels are indicated for a variable friction mechanism?
K 3
Describe the variable friction mechanism during initial swing
High friction to prevent excessive knee flexion
Describe the variable friction mechanism during midswing
Friction decreases to allow knee to swing easily
Describe the variable friction mechanism during terminal swing
Increase in friction for initial contact
Describe a manual locking knee mechanism
Single axis device. Provides stability through a physical lock on the knee until. Knee remains extended and stable when lock is engaged
Describe a weight activated knee mechanism
Single axis device with a friction brake that is activated by body weight. Unlocks as weight is relieved and swings freely during swing
What population will typically use a weight activated knee mechanism?
Elderly, low level ambulators who may need AT. Needs an extra degree of security while wearing the prosthesis