Which material is commonly used to create a rigid orthotic?

Acrylic is commonly used to create a rigid orthotic due to its excellent structural properties. It is a thermoplastic material that can be molded and shaped when heated and becomes rigid upon cooling. This rigidity offers significant support and stability, which is essential in the design of orthotic devices that aim to correct foot alignment and distribute weight evenly.

In contrast, EVA foam is primarily used for cushioning and shock absorption due to its softness and flexibility, making it less suitable for applications requiring rigidity. Plastazote is a lightweight and resilient foam that is often utilized for custom padding and softer orthotic needs, as it conforms to the foot's shape rather than providing a firm structure. Cork, while having some rigidity, is generally employed for cushioning and insulation, rather than being the primary choice for a completely rigid orthotic.

Thus, acrylic’s combination of moldability and rigidity makes it the ideal material for creating effective and supportive orthotic devices, which is why it is the correct choice.