CPT CPT Prosthetic Fitting & Alignment 2 — Questions and Answers
Question 1: What is 'check socket' used for in the prosthetic fitting process?
- To verify fit and alignment before fabricating the definitive socket (Correct answer)
- To test the strength of the final socket laminate
- To check infection in the residual limb
- To measure energy return of the prosthetic foot
Correct answer: To verify fit and alignment before fabricating the definitive socket
A check socket (test socket) is a transparent or temporary socket used to assess fit, comfort, and alignment prior to fabricating the permanent definitive socket.
Question 2: Which gait deviation is most commonly associated with a transtibial socket that is fit too loose?
- Pistoning during swing phase (Correct answer)
- Excessive knee flexion at midstance
- Vaulting on the sound side
- Lateral trunk bending toward the prosthetic side
Correct answer: Pistoning during swing phase
A loose socket causes pistoning—vertical movement of the limb within the socket during swing phase—reducing control and comfort.
Question 3: What does a 'total contact socket' design aim to achieve in lower-limb prosthetics?
- Distribute pressure evenly across the entire residual limb surface (Correct answer)
- Focus pressure on bony prominences for better control
- Reduce the weight of the prosthetic socket
- Allow air circulation around the residual limb
Correct answer: Distribute pressure evenly across the entire residual limb surface
Total contact socket design ensures the entire residual limb surface shares load evenly, reducing peak pressure points and improving patient comfort.
Question 4: When a prosthetist requests the technician to add a heel wedge to a SACH foot, what alignment adjustment does this typically create?
- Increased plantar flexion moment at heel strike (Correct answer)
- Increased dorsiflexion at midstance
- Reduced toe lever at terminal stance
- Decreased knee extension moment in early stance
Correct answer: Increased plantar flexion moment at heel strike
Adding a heel wedge compresses the heel cushion more, effectively increasing the plantar flexion moment at heel strike to assist knee stability.
Question 5: In a transfemoral prosthesis, excessive lateral trunk bending toward the prosthetic side during stance is most likely caused by which alignment fault?
- Socket positioned too far medially or abduction angle set incorrectly (Correct answer)
- Knee unit set with too much flexion
- Prosthetic foot dorsiflexion set too high
- Pylon length set too short
Correct answer: Socket positioned too far medially or abduction angle set incorrectly
Lateral trunk bending toward the prosthetic side indicates the socket is shifted medially or the hip abductor leverage is insufficient, often related to socket abduction angle.
Question 6: Which suspension system uses a shuttle lock mechanism where a pin attached to the liner clicks into a locking distal housing?
- Pin lock suspension (Correct answer)
- Suction suspension
- Elevated vacuum suspension
- Neoprene sleeve suspension
Correct answer: Pin lock suspension
Pin lock suspension systems feature a pin at the distal end of the liner that engages a ratchet-style lock in the socket, providing mechanical suspension.
CPT CPT Prosthetic Fitting & Alignment 2
What is 'check socket' used for in the prosthetic fitting process?