CPO Clinical Application & Fitting 2 — Questions and Answers
Question 1: During transtibial prosthetic fitting, a patient reports pistoning of the socket during ambulation. Which adjustment is most appropriate?
- Increase suspension by adding a pin lock or suction (Correct answer)
- Widen the proximal trim line
- Add distal padding to the socket
- Reduce socket volume by 10%
Correct answer: Increase suspension by adding a pin lock or suction
Pistoning indicates inadequate suspension, which is corrected by upgrading or adding a pin lock, suction sleeve, or elevated vacuum system.
Question 2: A patient with a transfemoral amputation experiences medial distal thigh pain during the stance phase. The most likely cause is:
- Excessive adduction of the socket
- Insufficient adduction of the socket (Correct answer)
- High lateral wall trim line
- Inadequate total contact
Correct answer: Insufficient adduction of the socket
Insufficient adduction leaves the femur in abduction, causing the distal medial femur to bear excess pressure against the socket wall.
Question 3: When fitting a PTB (patellar tendon bearing) socket, which anatomical landmark is considered the primary load-bearing area?
- Fibular head
- Patellar tendon (Correct answer)
- Tibial crest
- Medial tibial flare
Correct answer: Patellar tendon
The patellar tendon is the primary load-bearing area in a PTB socket due to its pressure tolerance and accessibility.
Question 4: A child with a below-knee limb deficiency is fitted with a prosthesis. The parent asks about growth management. The BEST practice is:
- Replace the prosthesis every 6 months regardless of fit
- Modify the socket with growth pads and schedule regular check-ups (Correct answer)
- Use adult-sized components to delay replacement
- Discourage prosthetic use until skeletal maturity
Correct answer: Modify the socket with growth pads and schedule regular check-ups
Children require regular monitoring with modular socket adjustments such as growth pads to accommodate growth without frequent full replacements.
Question 5: Which of the following best describes the function of a SACH (Solid Ankle Cushion Heel) foot?
- Stores and returns energy during push-off
- Simulates ankle motion through heel wedge compression (Correct answer)
- Provides dynamic response for high-activity users
- Allows multiaxial motion for uneven terrain
Correct answer: Simulates ankle motion through heel wedge compression
The SACH foot mimics ankle plantarflexion at heel strike through compression of a cushioned heel wedge, with no true articulation.
Question 6: For a patient with a Syme's amputation, the most important socket design consideration is:
- Providing a high proximal brim for suspension
- Accommodating the bulbous distal end while allowing donning (Correct answer)
- Positioning the knee joint anteriorly
- Maximizing socket volume to reduce weight bearing
Correct answer: Accommodating the bulbous distal end while allowing donning
The Syme's residual limb has a bulbous distal end requiring a socket with a removable panel or flexible inner socket to allow the bulge through for donning.
Question 7: A transfemoral patient ambulates with a lateral trunk lean toward the prosthetic side during stance. Which prosthetic cause should be investigated first?
- Excessive knee friction
- Short prosthetic length
- Insufficient socket adduction (Correct answer)
- Excessive dorsiflexion at the prosthetic ankle
Correct answer: Insufficient socket adduction
Insufficient socket adduction shifts the patient's center of mass laterally, causing the patient to lean over the prosthesis to maintain balance.
CPO Clinical Application & Fitting 2
During transtibial prosthetic fitting, a patient reports pistoning of the socket during ambulation.
Which adjustment is most appropriate?