CPO Clinical Application & Fitting 3 — Questions and Answers
Question 1: When conducting a dynamic alignment check for a below-knee prosthesis, the clinician observes early knee flexion at heel strike. The most likely cause is:
- Excessive dorsiflexion in the prosthetic foot (Correct answer)
- Heel cushion too firm
- Excessive plantarflexion in the prosthetic foot
- Socket placed too far anteriorly
Correct answer: Excessive dorsiflexion in the prosthetic foot
Excessive dorsiflexion in the foot moves the ground reaction force posterior to the knee, creating a knee flexion moment at heel strike.
Question 2: In upper limb prosthetics, body-powered hooks vs. myoelectric hands differ primarily in that myoelectric devices:
- Provide better proprioceptive feedback through cables
- Use EMG signals from residual limb muscles to control the terminal device (Correct answer)
- Are always lighter than body-powered systems
- Cannot grip objects weighing more than 2 kg
Correct answer: Use EMG signals from residual limb muscles to control the terminal device
Myoelectric prostheses detect surface EMG signals from residual limb muscles to control opening and closing of the terminal device without a harness.
Question 3: A patient with a unilateral transradial amputation is being fitted. The most critical measurement for socket fabrication is:
- Contralateral arm circumference at the elbow
- Residual limb length relative to the contralateral limb (Correct answer)
- Shoulder width and clavicle length
- Wrist circumference of the sound limb
Correct answer: Residual limb length relative to the contralateral limb
Residual limb length determines the available leverage for control and the prosthetic elbow placement relative to the contralateral side.
Question 4: A patient with diabetes and a transtibial amputation develops a reddened area over the fibular head after wearing their new prosthesis. The immediate action is:
- Prescribe oral antibiotics prophylactically
- Relieve socket pressure over the fibular head and reassess (Correct answer)
- Discontinue prosthetic use until the area resolves completely
- Apply a pressure bandage to the area
Correct answer: Relieve socket pressure over the fibular head and reassess
Redness over a bony prominence indicates excess pressure; the socket must be modified to relieve that area before skin breakdown occurs.
Question 5: Which spinal orthosis is most appropriate for a stable L1 compression fracture requiring immobilization without neurological involvement?
- Philadelphia collar
- TLSO (thoracolumbosacral orthosis) (Correct answer)
- LSO (lumbosacral orthosis)
- Milwaukee brace
Correct answer: TLSO (thoracolumbosacral orthosis)
A TLSO provides three-point pressure control across the thoracolumbar junction and is indicated for L1 fractures to restrict flexion, extension, and lateral bending.
Question 6: During gait analysis of a transfemoral amputee using a mechanical polycentric knee, the patient demonstrates excessive heel rise during swing phase. The most likely adjustment is:
- Increase extension assist
- Decrease swing-phase friction
- Increase swing-phase friction or extension assist (Correct answer)
- Add a stance-phase brake
Correct answer: Increase swing-phase friction or extension assist
Excessive heel rise during swing indicates insufficient friction or extension assist is preventing uncontrolled knee flexion as the limb swings forward.
Question 7: A 45-year-old patient with a transtibial amputation and K3 activity classification is being fit for the first time. Which foot category is most appropriate?
- SACH foot
- Single-axis foot
- Energy-storing/returning (dynamic response) foot (Correct answer)
- Multiaxial hydraulic ankle
Correct answer: Energy-storing/returning (dynamic response) foot
K3 patients (community ambulators with variable cadence) benefit from energy-storing dynamic response feet that support active walking and varied terrain demands.
CPO Clinical Application & Fitting 3
When conducting a dynamic alignment check for a below-knee prosthesis, the clinician observes early knee flexion at heel strike.
The most likely cause is: