Orthotic Device Design & Fabrication Flashcards

An orthotic shell fabricated by direct-contact molding over a positive cast is finished with a rough surface. Which tool is used FIRST to smooth the outer surface?

Answer: Belt sander or grinding wheel

A belt sander or grinding wheel quickly removes the bulk of surface roughness and excess plastic from the outer shell before finer finishing steps.

The 'subtalar neutral' casting technique for a custom foot orthosis requires the patient's subtalar joint to be positioned in:

Answer: 0° eversion/inversion (neutral alignment)

Subtalar neutral casting places the joint at its theoretical neutral position (equal talar head coverage medially and laterally) to capture an unbiased foot impression.

When riveting a leather-covered metal upright to a plastic shell, using a Chicago screw (binding post) instead of a solid rivet offers the advantage of:

Answer: Removability for repairs or adjustments

Chicago screws can be unscrewed for disassembly, making future repairs, component replacement, or adjustments much easier than with permanent solid rivets.

A patient with a high-arched (cavus) foot presents for a custom foot orthosis. The fitter should build in which intrinsic modification to offload the lateral forefoot?

Answer: Lateral forefoot flange and met pad

A lateral forefoot flange and metatarsal pad redistribute plantar pressure medially and reduce excessive loading under the lateral metatarsal heads common in cavus feet.

Which measurement is MOST critical when fitting a prefabricated knee orthosis to ensure the mechanical joint axis aligns with the anatomical joint?

Answer: Medial joint-line height from the floor

The medial joint-line height from the floor determines the correct vertical position of the orthosis hinge relative to the anatomical knee axis, preventing harmful shear forces.

When splinting an acute wrist fracture in a forearm-based orthosis, the orthotic material should be how long to provide adequate leverage?

Answer: Two-thirds the length of the forearm

A length of approximately two-thirds of the forearm provides sufficient lever arm to control wrist motion while remaining comfortable and not restricting elbow movement.

In the fabrication of a supra-malleolar orthosis (SMO), the trim line should extend just proximal to the:

Answer: Malleoli on both medial and lateral sides

The SMO trim line terminates just above the malleoli, capturing the ankle mortise to control hindfoot valgus/varus while leaving the leg free above the ankle.