CPT Prosthetic Components & Technology 2 — Questions and Answers
Question 1: Microprocessor-controlled prosthetic knees (MPKs) use onboard sensors primarily to assess which variables in real time?
- Socket pressure and residual limb temperature only
- Angular velocity, acceleration, and load data to modulate hydraulic resistance (Correct answer)
- Battery voltage and Bluetooth signal strength
- Patient heart rate and oxygen saturation
Correct answer: Angular velocity, acceleration, and load data to modulate hydraulic resistance
MPKs use gyroscopes, accelerometers, and load cells to continuously assess limb kinematics, then adjust hydraulic or pneumatic resistance to optimize gait.
Question 2: What type of wrist unit allows a transradial prosthesis user to pre-position the terminal device in multiple planes of rotation?
- Rigid wrist unit
- Flexion wrist unit with a single hinge
- Flexion-rotation wrist unit (flexion/extension and rotation) (Correct answer)
- Locking wrist unit only with extension
Correct answer: Flexion-rotation wrist unit (flexion/extension and rotation)
A flexion-rotation wrist unit provides both wrist flexion/extension and forearm rotation positioning, enabling the user to pre-set the terminal device for varied tasks.
Question 3: Which suspension method for a transtibial prosthesis relies on a urethane or silicone liner rolled onto the residual limb, with a locking pin that engages a clutch mechanism in the socket?
- Supracondylar cuff suspension
- Pin/lock (lanyard) suspension (Correct answer)
- Suction suspension with one-way valve
- Elevated vacuum suspension (EVS)
Correct answer: Pin/lock (lanyard) suspension
Pin/lock suspension uses a distal locking pin on the liner that clicks into a clutch or shuttle lock built into the distal socket, providing reliable mechanical suspension.
Question 4: Elevated vacuum suspension (EVS) systems improve prosthetic suspension and residual limb health primarily by:
- Adding mechanical locking pins at the distal end
- Maintaining negative pressure within the socket to reduce volume fluctuation and pistoning (Correct answer)
- Using supracondylar brim extensions to grip the femoral condyles
- Applying a neoprene sleeve over the proximal socket brim
Correct answer: Maintaining negative pressure within the socket to reduce volume fluctuation and pistoning
EVS actively evacuates air from the socket interface, creating consistent negative pressure that stabilizes residual limb volume, reduces pistoning, and improves proprioception.
Question 5: A myoelectric prosthetic hand uses surface electromyography (sEMG) signals from residual limb muscles to control the hand. Which muscle pair is most commonly used for transradial myoelectric control?
- Biceps brachii and triceps brachii
- Wrist flexors and wrist extensors (Correct answer)
- Pectoralis major and serratus anterior
- Deltoid anterior and deltoid posterior
Correct answer: Wrist flexors and wrist extensors
The wrist flexors and wrist extensors of the residual forearm are the primary electrode sites for transradial myoelectric control, as they retain voluntary muscle function distal to the amputation.
Question 6: In lower-limb prosthetics, a dynamic response (energy-return) prosthetic foot's carbon fiber keel primarily stores energy during which phase of gait?
- Initial contact and loading response (heel strike) (Correct answer)
- Mid-swing phase
- Terminal swing phase
- Pre-swing toe-off only
Correct answer: Initial contact and loading response (heel strike)
The carbon fiber keel deflects during loading response (heel strike to mid-stance), storing elastic energy that is subsequently released at toe-off to assist propulsion.
Question 7: Which feature distinguishes a multi-axial prosthetic foot from a single-axis foot?
- It is made entirely of carbon fiber with no moving parts
- It provides motion in the frontal plane (inversion/eversion) in addition to sagittal plane movement (Correct answer)
- It has a higher energy return coefficient than dynamic response feet
- It eliminates the need for a torsion adapter
Correct answer: It provides motion in the frontal plane (inversion/eversion) in addition to sagittal plane movement
Multi-axial feet allow inversion/eversion and transverse rotation in addition to plantarflexion/dorsiflexion, better accommodating uneven terrain and reducing socket stress.
CPT Prosthetic Components & Technology 2
Microprocessor-controlled prosthetic knees (MPKs) use onboard sensors primarily to assess which variables in real time?