CO Materials Science & Fabrication Techniques Flashcards

Which casting technique for a foot orthosis involves maintaining the subtalar joint in neutral position while allowing the forefoot to align naturally?

Answer: Non-weight-bearing subtalar neutral cast

The non-weight-bearing subtalar neutral cast captures the foot with the subtalar joint held in neutral, providing a biomechanically accurate model for custom orthosis fabrication.

What is the purpose of adding a metatarsal pad to a foot orthosis?

Answer: To offload the metatarsal heads by redistributing pressure proximally

A metatarsal pad placed proximal to the metatarsal heads redistributes pressure away from them, alleviating pain from metatarsalgia or Morton's neuroma.

Closed-cell foam such as Plastazote is commonly used as an orthotic interface material primarily because it:

Answer: Is heat-moldable and provides cushioning with pressure distribution

Plastazote is a closed-cell polyethylene foam that can be heat-molded to conform to the foot and provides excellent cushioning and pressure distribution for insensate or painful feet.

A rectified positive model is used in orthotic fabrication to:

Answer: Modify the plaster cast to build in corrections or accommodations before forming the device

A rectified positive model is a plaster model that has been modified by adding or removing material to build in the desired biomechanical corrections before the orthosis is formed over it.

Which rivet or fastener type is most appropriate for attaching metal uprights to a leather orthotic foundation to allow articulation?

Answer: Chicago screw (sex bolt)

Chicago screws (sex bolts) are ideal for orthotic joints because they can be tightened to control resistance to motion and can be replaced if worn, unlike solid rivets.

What is the primary reason stainless steel alloys are preferred over aluminum alloys for load-bearing orthotic uprights in heavier patients?

Answer: Stainless steel has greater yield strength and fatigue resistance under high loads

Stainless steel has higher yield strength and superior fatigue resistance compared to aluminum, making it the appropriate choice for uprights that must bear significant repetitive loads without deforming.