Orthotics and Prosthetics

The use of orthotic devices varies in a fairly significant way depending on the training and background of the prescribing practitioner.

• Various practitioners, including orthopaedic surgeons, podiatrists, physical therapists, and more, prescribe orthotics for various pathologies, and there are widely varying opinions about best practices.

• With that being said, there are pathologies that unquestionably benefit from orthotics, and there are many themes in terms of types on inserts that are appropriate.

In certain pathologies, orthotic devices are an indispensable component of nonoperative treatment.

• A stiff insert can be beneficial in hallux rigidus as well as midfoot arthritis and in recovery from metatarsal stress fractures.

• Metatarsalgia ± hammer toes can be treated with a metatarsal pad often with some success. The accompaniment of a Budin splint may impart a greater success rate.

• An arch support of some description is typically a large part of nonoperative treatment for the symptomatic flatfoot.

• A cavus foot with a supple hindfoot may be manipulated into a better position with a relief underneath the 1st metatarsal head.

Differences of opinion with regard to orthotics largely center over the relative ubiquity of their need, i.e., many practitioners agree that their directed use is appropriate, while promoting them as a panacea for all manner of ills is likely inappropriate.

Orthosis is an externally applied device used to modify the structural or functional characteristics of the musculoskeletal system, an apparatus used to support, align, prevent, or correct deformities or to improve the function of movable parts of the body.

During static stance and ambulation, the lower extremities are subjected to external forces and moments. During normal function, these forces and moments are resisted or controlled by internal structures of the body. When internal structures fail, orthoses can modify external forces and moments to allow the body to function in a “normal” manner.

An external device used to support or improve function of the foot and ankle can take many physical forms, from a simple felt pad to a composite brace controlling foot and ankle motions. Orthotics prescribed for lower extremity pathologies include foot orthoses (FOs), ankle-foot orthoses (AFOs), knee orthoses, and knee-ankle-foot orthoses.

Various types of orthoses are commonly prescribed for foot and ankle pathologies. The basic subcategories of FOs are prefabricated and custom. There are clear differences between the manufacture and design of orthoses in each category, yet advantages or benefit of one type of device over another has yet to be proven.

• Prefabricated devices have the distinct benefit of lower cost compared with custom-fabricated foot orthotics. In addition, prefabricated orthoses can be readily stocked for immediate dispensing to the patient. The disadvantage of prefabricated orthotic devices is their difficulty in application to limb and foot shapes that fall outside the “average” range.

• Custom molding and contouring of an orthotic device to a body segment may be the critical feature necessary for a successful treatment outcome. Yet the mechanism by which foot orthotics actually achieve their treatment effects remains poorly understood, and, thus, claims of superiority of custom vs. prefabricated devices remain speculative.

Prefabricated FOs are available for a wide variety of clinical application. In general, these devices are used to offload specific areas of the foot, cushion the foot from impact, support the medial longitudinal arch, and provide mild biomechanical control of hindfoot movements.

Custom FOs can be either accommodative or functional.

• Functional orthoses are most often used with flexible feet, working to alter how foot meets floor.

• Accommodative orthoses generally are used with more rigid deformities; rather than attempting to alter foot alignment, accommodative orthoses work to relieve pressure under bony prominences.

The simplest types of prefabricated FOs are in-shoe pads. Felt forefoot pads are available to relieve metatarsalgia, sesamoiditis, and intractable plantar keratoses. These adjust pressure by offloading adjacent areas and increasing pressure under the pad itself. They are often placed near, but not directly under, the area of pain.

Contoured cushioned prefabricated insoles have a wide variety of clinical application for relief of plantar foot pressures, dissipation of impact shock, and enhancement of overall foot comfort. These contoured insoles function as a softer version of a prefabricated arch support.

Prefabricated, “biomechanical” semirigid foot orthotics are made from materials commonly used in the fabrication of more expensive custom functional FOs. These devices are contoured to an average shape of a medial and lateral longitudinal arch and generally lack any heel cup. Sometimes, posting is provided in the hindfoot to enhance pronation control.

The goal of treatment of these devices is to provide more rigid support and motion control than with softer arch supports.

Custom foot orthotic devices require fabrication to some type of model of the patient’s foot. The model on which the orthosis is contoured can be a positive plaster cast, a computer-generated model, or the actual foot of the patient.

Equally important to the value of any custom foot orthotic is the selection of material composition, which will be unique to the patient’s clinical condition or biomechanical needs.

Accommodative FOs are designed to relieve pressure on certain areas of the foot and to provide support of the foot in its compensated position. The most common use for accommodative foot orthotics is in the management of diabetic foot complications. These devices are also known as total contact orthoses and can disperse plantar pressures to the maximal foot surface area.

Functional FOs are designed to control forces that act on the foot during the stance phase of gait. These forces are generally inversion/eversion &/or rotatory forces acting on the subtalar and midtarsal joints.

While not part of the definition, functional FOs are often expected to correct alignment of the foot. Yet improvements of alignment with functional FOs are relatively modest, as revealed by numerous kinematic studies of these devices. Kinetic studies of FOs have confirmed that these devices can alter forces or moments acting on the joints of the lower extremity.

A predecessor to the functional FO was the University of California Biomechanics Laboratory orthosis (UCBL). This device is still popular today in the treatment of flatfoot conditions. The UCBL is a plastic FO with a deep heel cup and steep medial and lateral flanges. The UCBL is best suited to control transverse plane subluxation of the foot by applying force against the lateral wall of the calcaneus, sustentaculum tali, and lateral aspect of the 5th metatarsal shaft. These devices have fallen out of favor due to difficulty with shoe fit and the need for multiple adjustments for comfort.

Functional FOs were developed in the early 1960s. Several principles apply to functional orthotic development. Semirigid to rigid materials are utilized to control significant forces that occur in most foot pathologies. A mold is made of the foot to which posting can be added to address the individual deformity present.

The majority of studies of treatment effects of FOs have significant deficiencies that must be noted before any conclusions or recommendations can be made. Many studies are simple retrospective “patient satisfaction” surveys, and higher levels of evidence are generally lacking. In most cases, the type of orthosis is not described in detail, and descriptions of the foot types of the subjects are often lacking.