Orthosis
An orthosis (plural: orthoses) is “an externally applied device used to modify the structural and functional characteristics of the neuromuscular and skeletal system. An orthosis may be used to:
- Control, guide, limit and/or immobilize an extremity, joint or body segment for a particular reason
- To restrict movement in a given direction
- To assist movement generally
- To reduce weight bearing forces for a particular purpose
- To aid rehabilitation from fractures after the removal of a cast
- To otherwise correct the shape and/or function of the body, to provide easier movement capability or reduce pain
Manufacture and materials
Orthoses were traditionally made by following a tracing of the extremity with measurements to assist in creating a well fitted device. Later the advent of plastics as a material of choice for construction necessitated the idea of creating a mold of the body part in question. Orthoses are made from various types of materials including thermoplastics, carbon fiber, metals, elastic, fabric or a combination of similar materials. Some designs may be purchased at a local retailer; others are more specific and require a prescription from a physician, who will fit the orthosis according to the patient’s requirements. Over-the-counter braces are basic and available in multiple sizes. They are generally slid on or strapped on with Velcro, and are held tightly in place. One of the purposes of these braces is injury protection.
Classification
Orthoses are classified by an acronym describing the anatomical joints which they contain. For example, an ankle foot orthosis (‘AFO’) is applied to the foot and ankle, a thoracolumbosacral orthosis (‘TLSO’) affects the thoracic, lumbar and sacral regions of the spine. It is also necessary to describe the function of the orthosis.
Lower-limb orthoses
A lower-limb orthosis is an external device applied to a lower-body segment to improve function by controlling motion, providing support through stabilizing gait, reducing pain through transferring load to another area, correcting flexible deformities, and preventing progression of fixed deformities.
Ankle-foot orthosis (AFO) An ankle-foot orthosis (AFO) is an orthosis or brace (usually plastic) that supports the ankle and foot. AFOs are externally applied and intended to control position and motion of the ankle, compensate for weakness, or correct deformities. AFOs can be used to support weak limbs, or to position a limb with contracted muscles into a more normal position. They are also used to immobilize the ankle and lower leg in the presence of arthritis or fracture, and to correct foot drop; an AFO is also known as a foot-drop brace. No evidence exists to support the concern that using an orthosis will keep neurologic repair from taking place. Ankle-foot orthoses are the most commonly used orthoses, making up about 26% of all orthoses provided in the United States. An AFO is generally constructed of lightweight polypropylene-based plastic in the shape of an “L”, with the upright portion behind the calf and the lower portion running under the foot. They are attached to the calf with a strap, and are made to fit inside accommodative shoes. The unbroken “L” shape of some designs provides rigidity, while other designs (with a jointed ankle) provide different types of control. Obtaining a good fit with an AFO involves one of two approaches:
- provision of an off-the-shelf or prefabricated AFO matched in size to the end user
- Custom manufacture of an individualized AFO from a positive model, obtained from a negative cast or the use of computer-aided imaging, design, and milling. The plastic used to create a durable AFO must be heated to 400°F., making direct molding of the material on the end user impossible