Orthotic Device Design & Fabrication Flashcards

A wrist-hand orthosis (WHO) intended to immobilize the wrist in neutral should position the wrist at approximately:

Answer: 0–10° extension

A functional or resting WHO is typically fabricated with the wrist in neutral to slight extension (0–10°) to maintain a functional hand position and prevent contracture.

When selecting polypropylene sheet thickness for a pediatric foot orthosis for a child weighing 20 kg, the fitter should choose:

Answer: 3/16 inch (4.8 mm)

A 3/16-inch (4.8 mm) polypropylene sheet provides adequate rigidity for a child around 20 kg without being unnecessarily heavy or stiff.

The 'University of California Biomechanics Laboratory' (UCBL) insert is designed primarily to control:

Answer: Subtalar valgus and hindfoot pronation

The UCBL insert features deep heel cup walls that capture the calcaneus and control excessive subtalar eversion (hindfoot valgus/pronation).

A fitter is using a heat gun to spot-heat a thermoplastic orthosis for minor adjustments. At what distance should the heat gun be held to avoid burning the material?

Answer: 6–8 inches (15–20 cm)

Holding the heat gun 6–8 inches away concentrates heat enough to soften a small area without scorching or distorting adjacent material.

Which edge-finishing technique BEST reduces the risk of skin abrasion along the proximal trim line of a hard plastic AFO?

Answer: Flaring and flame-polishing the edge

Flaring the proximal edge outward and then flame- or belt-polishing it removes sharp burrs and creates a smooth, rolled edge that is less likely to abrade the skin.

In fabricating a custom thoracic-lumbar-sacral orthosis (TLSO), what is the purpose of adding a polyethylene foam liner inside the rigid shell?

Answer: Distribute pressure and improve comfort at bony prominences

A foam liner distributes contact forces over a larger area, protecting bony prominences such as the iliac crests and ribs from pressure injuries.

When carbon fiber is used instead of polypropylene for an AFO shell, the primary clinical benefit is:

Answer: Higher stiffness-to-weight ratio allowing a thinner, lighter device

Carbon fiber composites offer superior stiffness per unit weight compared to polypropylene, enabling thinner, lighter orthotic shells without sacrificing structural support.