The Casting Fabrication Techniques of AFO

An AFO or ankle-foot orthosis provides patients with support for weak or wasted limbs by positioning the foot, ankle and leg in the proper position. Patients with tight, contracted muscles could benefit from an AFO, as well as patients with foot drop, stroke damage, cerebral palsy or sprain. A doctor may recommend an AFO for a patient with an unstable ankle, flat feet, or a foot and ankle with painful motion.

Prep Work

• A technician custom builds the AFO for the patient. The custom design is based on a negative cast design -- a mold built by pouring plaster or other molding compound into a cast that was constructed on the patient's leg and then cut off and allowed to dry. This allows the technician to have a perfect replica of the leg, ankle and foot without having to have the patient there in the office.

  The technician follows the recommendations of the doctor to determine the particular design of the AFO. There are five different kinds of AFO and the fabrication technician will need to know exactly what kind of orthotic to cast. Computer design techniques are used to determine the specifics of each casting and milling; minor corrections can be made to the design before fabrication.

Creating the Cast

• The patient puts on a stockinette prior to the construction of the cast. This prevents the cast from adhering to the skin. The orthotics technician (or doctor, in some cases) places the foot and ankle in the most neutral position possible and begins wrapping the cast material around the patient's limb. The cast should reflect the optimal position of the patient's limb to provide the best possible support and reduce the need to adjust the AFO design before fabrication.

  After the cast is wrapped around the patient's limb, the technician marks any landmarks or problem areas on the outside of the cast to alert the fabrication technician to specific points of concern. The cast is also marked with the name of the medical practice and doctor and the name of the patient. This prevents confusion or mix up at the fabrication company.

Final Casting Steps

• The cast is carefully cut off the patient leg. Strips of casting material will be placed on the outside of the cast to seal it back into position.

  The cast is then allowed to dry upright. This prevents the cast from deforming while it dries and makes the cast lighter to ship. The cast is then shipped to the orthotics manufacturer who uses it to custom-build the AFO.

AFO Construction

• The core of the AFO is constructed most often of thermoplastics. Thermoplastics are preferred because they retain their shape even if the cast is reheated, and allow for high-stress activities like walking and running. Other materials on the AFO may include metal hinging, leather or synthetic fabric cover and lacing.