Suspension methods for BK

Question 1

Patellar Tendon Bearing (PTB)

Answer 1

Advantages:
1. Utilize pressure tolerant areas
2. Avoid pressure sensitive areas

Disadvantages:
1. Does not provide even distribution of forces across the limb
2. Certain pathologic conditions also negate it’s use.

Question 2

Cuff Suspension

Primary indication: Anticipate residual limb volume changes

Answer 2

Advantages:
1. Adjustability (with velcro closure)
2. Ease of donning and doffing by the patient
3. Adequate suspension for the majority of transtibial amputees
4. Provides moderate control of knee extension
5. Easily replaced

Disadvantages:
1. Cannot completely eliminate socket pistoning.
2. During knee flexion, may pinch soft tissue between the posterior proximal end of the socket brim and the cuff.
3. May restrict circulation.
4. Provides no added ML stability

Question 3

Waist Belt Suspension

Answer 3

Advantages:
1. Much of the weight of the prosthesis is distributed proximally over the iliac crests
2. Enables patients to loosen the supracondylar cuff or other form of suspension.
3. Good auxillary aid when other types of suspension are inadequate
4. The elastic strap provides some knee extension assistance

Disadvantages:
1. Discomfort of wearing a belt
2. Does not provide even suspension through swing phase (the tension of the elastic is proportional to the degree of knee flexion)
3. The fork strap does not provide any resistance to knee extension
4. No ML stability is provided by waist belt suspension alone.

Question 4

PTB Supracondylar suprapatellar suspension (SCSP)

Primary Indication: Knee instability or ligament laxity a secondary factory, shorter limb length, when limb needs more ML stability than cuff suspension

Answer 4

Advantages:
1. Suspension is an inherent part of the socket
2. Is less restrictive to circulation than part of the socket
3. SC wedge aids in knee stability, rotational control, and pressure distribution. Controls ligament laxity.
4. Reduces pistoning
5. Still able to don and doff with limited and function or vision compared to cuff or gel liner
6. Suprapatellar extension limits knee hyperextension

Disadvantages:
1. Modifications over the patella and femoral condyles must be precisely located
2. Enclosure of the patella can inhibit comfortable kneeling
3. May be less cosmetic and more destructive to clothing because higher trim lines protrude when the knee is flexed
4. May restrict full knee flexion
5. suspension pressure is localized

Question 5

Sleeve Suspension

Primary indication: Used as secondary suspension, may be used as primary suspension with PTB socket with sock fit or cushion liner (typically have one way valve to expel air)

Answer 5

Advantages:
1. Simple and effective means of suspension
2. Helps minimize socket pistoning
3. good auxiliary suspension
4. does not create proximal constriction

Disadvantages:
1. Provides no added knee stability
2. Suspension is greatly decreased if the sleeve is punctured
3. Perspiration may build up under the sleeve and create skin irritation or hygiene problems
4. Must be replaced regularly
5. Sleeves may restrict full knee flexion
6. Requires good hand function to don and doff

Question 6

Gel Liner with suction / Vacuum socket

Primary Indication: added cushion, reduce shear forces

Answer 6

Advantages:
1. Improved suspension, decrease pistoning
2. Increased range of motion in flexion
3. Decreased shear on residual limb
4. Works best with stable limbs.
5. Improved proprioception (due to the seal created to the socket)
6. Improves patient health of limb by providing distribution of forces

Disadvantages:
1. Some patients may have difficulty in donning the liner
2. Punctures or tears in the silicone can dramatically decrease suction suspension
3. Perspiration
4. Patient has to have volume stability
5. Limitations of life span and durability of seals and liners

Question 7

Joints and thigh Corset

Primary Indication: damaged knee or residual limb can’t bear pressures

Answer 7

Advantages:
1. Provides maximum ML stability
2. Can provide maximum prevention of recurvatum
3. redistributes some weight bearing and torque forces to the thigh
4. increases proprioceptive feedback

Disadvantages:
1. Can contribute to distal edema
2. Tends to atrophy thigh musculature
3. Leather is no very hygienic
4. Joint centers must be precisely located to minimize motion between the leg and the prosthesis
5. Adds weight and bulk to the prosthesis. Awkward to don.
6. Not very cosmetic
7. Requires more fabrication time
8. Usually requires additional suspension of a fork strap and waist belt
9. Allows for pistoning if lacer is not tight enough