Prosthetic & Orthotic Design & Fabrication Flashcards

Which thermoforming technique is most appropriate for fabricating a total contact orthosis requiring high conformity to bony prominences?

Answer: Vacuum forming over a positive model

Vacuum forming over a positive model applies uniform negative pressure to draw the heated thermoplastic into intimate contact with all surface contours.

A patient with a transfemoral amputation has a residual limb that has decreased in volume significantly post-surgery. Which socket modification is the FIRST step to address this?

Answer: Add distal padding or liner inserts

Adding distal padding or liner inserts compensates for volume loss and restores fit without the expense and time of fabricating a new socket.

In carbon fiber laminate fabrication, the direction of fiber orientation most critical for maximizing longitudinal stiffness in a pylon is:

Answer: 0° (parallel to long axis)

Fibers oriented at 0° (parallel to the long axis) bear axial loads most efficiently, maximizing longitudinal stiffness.

When casting a patient for a below-knee orthosis, the subtalar joint should ideally be positioned in:

Answer: Neutral subtalar position

Casting in subtalar neutral captures the foot in its most biomechanically efficient alignment, which is the goal for most AFO designs.

Which material property makes high-density polyethylene (HDPE) preferable over polypropylene for a patient requiring frequent impact loading in a lower-limb orthosis?

Answer: Higher impact resistance and toughness

HDPE's higher impact resistance and toughness make it better able to absorb repeated impact loads without fracture compared to polypropylene.

A transtibial prosthetic socket with a roll-on liner and locking pin achieves suspension primarily through:

Answer: Mechanical engagement of pin into a locking mechanism

The pin at the distal end of the roll-on liner clicks into a lock in the socket, providing suspension via mechanical engagement.

Which of the following best describes the purpose of a relief in a prosthetic socket over a bony prominence?

Answer: To reduce pressure concentration over sensitive areas

Reliefs are recessed areas in the socket that offload pressure from sensitive or bony structures, preventing tissue breakdown.