Orthotic and Prosthetic Design & Fabrication Flashcards

Which thermoplastic is most commonly chosen for custom AFOs because of its fatigue resistance and moldability?

Answer: Polypropylene

Polypropylene resists repeated flexing without cracking, making it the standard AFO material.

Compared with homopolymer polypropylene, copolymer polypropylene (with added ethylene) is:

Answer: More flexible and more impact resistant

Ethylene content increases flexibility and toughness while reducing stiffness.

The main reason carbon fiber is added to a laminated prosthetic socket is to provide:

Answer: High stiffness with low weight

Carbon fiber offers an excellent stiffness-to-weight ratio for structural reinforcement.

Which reinforcement fabric is known for high tensile and impact strength but is very difficult to cut and sand?

Answer: Kevlar (aramid)

Aramid fibers are extremely tough, which makes trimming and finishing laminations difficult.

Increasing the ratio of flexible to rigid acrylic resin in a lamination will result in a laminate that is:

Answer: More flexible and less rigid

Flexible resin increases compliance of the finished laminate.

Which material is most commonly used to fabricate a soft insert liner for a transtibial socket?

Answer: Closed-cell polyethylene foam (Pelite)

Pelite is moldable, closed-cell, and durable, making it the classic soft insert material.

Adding corrugations to a thermoplastic AFO at the ankle primarily serves to:

Answer: Increase stiffness in that region

Corrugations increase the area moment of inertia, stiffening the plastic locally.