Orthosis

The term Orthosis is derived from “ortho”, meaning to straighten, and is concerned with the design, development, fitting and manufacturing of orthoses, which are devices that support or correct musculoskeletal deformities and/or abnormalities of the human body. Differing orthoses may directly support the lower limb, upper extremity, or the spine. However, Footwear Consultants and our Board Certified Pedorthist focus on Ankle-Foot Orthsis, involving devices made specifically to aid in the health of the foot.

Ankle-foot orthoses (AFOs) are orthoses or braces, usually plastic, encompassing the ankle joint and all or part of the foot. AFOs are externally applied, and are intended to control position and motion of the ankle, compensate for weakness, or correct deformities. They control the ankle directly, and can be designed to support the knee joint indirectly as well.

AFOs are commonly used in the treatment of disorders that affect muscle function such as diabetes, stroke, spinal cord injury, muscular dystrophy, cerebral palsy, polio and multiple sclerosis. AFOs can be used to provide support to weak or deformed limbs, or to position a limb with tight, 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 may also be referred to as a foot-drop brace.

Background

The use of generic descriptions of orthopedic braces, such as ankle foot orthosis, began in the late 1970s as the result of work done by the American Academy of Orthopedic Surgeon in order to make classification of such braces easy. The initial description in the literature of the device now referred to as an ankle foot orthosis was made by York, et al., in the late 1960s. Prior to that time, braces that supported the lower leg were limited to metal and leather designs attached to the shoe or plaster casts, called short leg braces or short leg casts.

Fabrication

Obtaining a good fit with an AFO involves one of two approaches:

1) Provision of an off-the-shelf or prefabricated AFO matched in size to the end user

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2) Custom manufacture of an individualized AFO from a positive model obtaining by means of a negative cast or the use of computer assisted imaging, design, and milling. The plastic used to create a durable AFO must be heated to 400 degrees Fahrenheit, making direct molding of the material on the end user impossible.

There are four major types of AFOs. Flexible AFOs may provide dorsiflexion assistance, but give poor stabilization of the subtalar joint. Anti-Talus AFOs block ankle motion, especially dorsiflexion, but also do not provide good stabilization for the subtalar joint. Rigid AFOs do block ankle movements and stabilize the subtalar joint, and may also help control adduction and abduction of the forefoot. AFOs made with the Tamarack Flexure Joint, however, provide subtalar stabilization while allowing free ankle dorsiflexion and free or restricted plantar flexion, depending upon the design. AFOs made with a special version of this joint may even provide dorsiflexion assistance to correct foot drop.