Orthotic Materials & Fabrication Techniques Flashcards

Which property of low-temperature thermoplastics (LTT) makes them particularly useful for upper-extremity orthoses fabricated directly on the patient?

Answer: They soften at temperatures safe for skin contact (around 60–70°C) and conform directly to the patient

LTTs soften at temperatures safe for direct skin contact, allowing the therapist or technician to mold them directly on the patient for precise conformity.

In metal upright fabrication for a KAFO, which process is used to form a contoured shape in the metal upright to follow the anatomy of the limb?

Answer: Annealing and bending with a bending iron

Annealing softens the metal and bending with a bending iron allows the upright to be contoured to match limb anatomy without cracking.

What does the term 'check socket' refer to in orthotic and prosthetic practice?

Answer: A transparent or preliminary test socket used to verify fit before fabricating the definitive device

A check socket is a diagnostic/test socket, often made from transparent thermoplastic, used to evaluate fit and alignment before fabricating the final device.

Which surface treatment improves adhesion when bonding two polypropylene surfaces together using contact cement?

Answer: Sanding the surface with coarse grit paper to roughen it

Roughening the polypropylene surface with coarse sandpaper increases surface area and mechanical interlocking sites, significantly improving adhesive bond strength.

When fabricating a wrist-hand orthosis (WHO) from low-temperature thermoplastic, which wrist position is most commonly used for a resting hand splint?

Answer: Wrist in 20–30° extension, MCPs in 45–70° flexion, IPs slightly flexed, thumb abducted

The intrinsic-plus or safe position (wrist 20–30° extension, MCPs flexed, IPs extended) prevents contracture and is the standard for resting hand splints.

Which characteristic distinguishes open-cell foam from closed-cell foam in orthotic applications?

Answer: Open-cell foam absorbs moisture and compresses more readily; closed-cell foam resists moisture and holds its shape longer

Open-cell foam absorbs sweat and compresses more quickly (bottoms out), while closed-cell foam resists moisture and maintains its cushioning properties longer.

During resin lamination, what is the role of the catalyst (hardener) added to polyester or epoxy resin?

Answer: To initiate the chemical cross-linking reaction that hardens the resin

The catalyst (hardener) initiates the exothermic cross-linking (polymerization) reaction that converts liquid resin into a rigid, durable thermoset composite.