Orthotics

Orthotics (Greek: Ορθός, ortho, "to straighten" or "align") is a specialty within the medical field concerned with the design, manufacture and application of orthoses. An orthosis (plural: orthoses) is "an externally applied device used to modify the structural and functional characteristics of the neuromuscular and skeletal system".[1] 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

Orthotics combines knowledge of anatomy and physiology, pathophysiology, biomechanics and engineering. Patients benefiting from an orthosis may have a condition such as spina bifida or cerebral palsy, or have experienced a spinal cord injury or stroke. Equally, orthoses are sometimes used prophylactically or to optimise performance in sport.
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 plaster of Paris mold of the body part in question. This method extensively is still used throughout the industry. Currently CAD/CAM, CNC machines and even 3D printing[2] are involved in orthotic manufacture.
Orthoses are made from various types of materials including thermoplastics, carbon fibre, 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.[3]
Classification
Under the International Standard terminology, orthoses are classified by an acronym describing the anatomical joints which they contain.[4] 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 useful to describe the function of the orthosis. Use of the International Standard is promoted to reduce the widespread variation in description of orthoses, which is often a barrier to interpretation of research studies.[5]

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.[7]

Foot orthoses

Foot orthoses comprise a specially fitted insert or footbed to a shoe. Also commonly referred to as "Orthotics" these orthoses provide support for the foot by distributing pressure or realigning foot joints while standing, walking or running. A great body of information exists within the podiatry and pedorthotic community describing the sciences that might be used to aid people with foot problems as well as the impact "orthotics" can have on knee, hip, and spine conditions. As such they are often used by athletes to relieve symptoms of a variety of soft tissue inflammatory conditions like plantar fasciitis.[8] They may also be used in conjunction with properly fitted orthopedic footwear in the prevention of foot ulcers in the at-risk diabetic foot.

Ankle-foot orthosis (AFO)

1

An AFO worn on the left foot with ankle hinge

2

Schematic ankle-foot orthosis
An ankle-foot orthosis (AFO) is an orthosis or brace that encumbers 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. Ankle-foot orthoses are the most commonly used orthoses, making up about 26% of all orthoses provided in the United States.[9] According to a review of Medicare payment data from 2001 to 2006, the base cost of an AFO was about $500 to $700.[10] 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:

  1. provision of an off-the-shelf or prefabricated AFO matched in size to the end user
  2. 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.

The International Red Cross recognizes four major types of AFOs:

Flexible AFOs

Anti-Talus AFOs

Rigid AFOs

Tamarack Flexure Joint

may provide dorsiflexion assistance, but give poor stabilization of the subtalar joint.

block ankle motion, especially dorsiflexion; do not provide good stabilization for the subtalar joint.

block ankle movements and stabilize the subtalar joint; may also help control adduction and abduction of the forefoot.

provide subtalar stabilization while allowing free ankle dorsiflexion and free or restricted plantar flexion. Depending upon the design; may provide dorsiflexion assistance to correct foot drop.[11]

The International Committee of the Red Cross published its manufacturing guidelines for ankle-foot orthoses in 2006.[11] Its intent is to provide standardized procedures for the manufacture of high-quality modern, durable and economical devices to people with disabilities throughout the world.