CPT Maintenance, Repairs, & Quality Assurance 2 — Questions and Answers
Question 1: When inspecting a transtibial prosthetic socket for wear, which area is MOST prone to stress cracking in a laminated socket?
- The proximal brim trim line (Correct answer)
- The pylon attachment interface
- The distal end cap junction
- The medial wall mid-section
Correct answer: The proximal brim trim line
The proximal brim trim line experiences the greatest cyclical stress during donning and doffing, making it the most common site for stress cracks in laminated sockets.
Question 2: A patient reports that their endoskeletal prosthetic knee makes a clicking noise only during swing phase. The MOST likely cause is:
- Worn extension bumper or stop (Correct answer)
- Loose pylon set screws
- Degraded hydraulic fluid
- Cracked proximal socket wall
Correct answer: Worn extension bumper or stop
A clicking sound specifically during swing phase is characteristic of a worn or deteriorated extension bumper or stop reaching end range of motion.
Question 3: Which solvent is most appropriate for cleaning residual adhesive from a carbon fiber socket before re-lamination?
- Acetone
- Mineral spirits
- Isopropyl alcohol (Correct answer)
- Methyl ethyl ketone (MEK)
Correct answer: Isopropyl alcohol
Isopropyl alcohol effectively removes adhesive residue without degrading carbon fiber or epoxy matrix materials used in prosthetic sockets.
Question 4: During a quality check of a new SACH foot, the technician notices the keel extends too far distally. This error will MOST likely cause:
- Increased toe stiffness limiting late stance energy return (Correct answer)
- Pistoning of the socket during mid-stance
- Excessive knee flexion at initial contact
- Vaulting during swing phase
Correct answer: Increased toe stiffness limiting late stance energy return
A keel extending too far distally increases toe lever arm stiffness, restricting terminal stance rollover and reducing energy return.
Question 5: A transfemoral prosthesis with a suction suspension system is leaking air at the valve housing. After replacing the valve, the appropriate QA check is to:
- Submerge the socket in water and pressurize to check for bubbles
- Have the patient ambulate and report perceived suction loss
- Apply soapy water around the valve and listen for hissing (Correct answer)
- Measure the socket volume with a calibrated fluid displacement tool
Correct answer: Apply soapy water around the valve and listen for hissing
Applying soapy water around the valve housing and watching for bubble formation is the standard bench test to verify an airtight seal after valve replacement.
Question 6: The recommended torque specification for tightening a standard 4-hole pyramid adapter to a pylon in most endoskeletal systems is typically found in:
- The component manufacturer's technical documentation (Correct answer)
- The ABC credentialing standards handbook
- The patient's initial evaluation form
- The facility's general maintenance log
Correct answer: The component manufacturer's technical documentation
Torque specifications are component-specific and must always be sourced from the individual manufacturer's technical documentation to prevent under- or over-tightening.
Question 7: A patient's prosthetic foot shell develops a visible crack along the lateral border after six months of use. The FIRST step a technician should take is:
- Document the damage and assess whether structural integrity is compromised (Correct answer)
- Immediately replace the entire prosthetic foot component
- Apply epoxy resin to the crack and return the device to the patient
- Sand the cracked area smooth and continue monitoring
Correct answer: Document the damage and assess whether structural integrity is compromised
The technician must first document and assess whether the crack is cosmetic or structural before determining the appropriate repair or replacement action.
CPT Maintenance, Repairs, & Quality Assurance 2
When inspecting a transtibial prosthetic socket for wear, which area is MOST prone to stress cracking in a laminated socket?