Foot orthoses are an important part of the medical treatment which podiatrists offer for their patients with foot and lower extremity pathology. In most communities, podiatrists are still perceived as the healthcare providers who are most qualified at providing quality foot orthoses to the public. However, if you were asked by a representative of a managed care organization or by a representative of your local, state or federal government what the definition of a foot orthosis is, could you provide them with one? Even though we all basically know what a foot orthosis is, do we really have a meaningful and currently accurate definition of a foot orthosis? As more healthcare providers start offering foot orthoses as part of their services, it becomes increasingly more important for podiatrists to become aware of the most current information regarding foot orthoses so that they can remain the most knowledgeable healthcare providers in the field of foot and lower extremity biomecha nics and the therapeutic use of foot orthoses.
Dorland’s Illustrated Medical Dictionary, 25th edition, defines an orthosis as "an orthopedic appliance or apparatus used to support, align, prevent, or correct deformities or to improve the function of movable parts of the body." Even though this is a good general definition of orthoses, the definition needs to be more specific to accurately describe its intended function in the treatment of foot and lower extremity pathology.
Kent Wu, an orthopedic surgeon who writes and lectures extensively on the evaluation and treatment of foot disorders, offered the following definition of a foot orthosis: "a foot orthosis is a medical device employed to support and align the foot, to prevent or correct foot deformities, or to improve the functions of the foot" (Wu, Kent K.: Foot Orthoses: Principles and Clinical Applications. Williams and Wilkins, Baltimore, 1990, p. 97). I like this definition in that it describes, more specifically, the function of a foot orthosis, but I don’t agree that a foot orthosis truly corrects foot deformities. In addition, the definition of a foot orthosis should include some reference as to the prevailing opinion of how foot orthoses actually work to relieve symptoms and improve the function of the foot and lower extremity.
The best definition of a foot orthosis that I have seen in the medical literature comes from Ray Anthony, a podiatrist who owns a foot orthosis laboratory in England. Anthony provided a definition for functional foot orthoses in a book he wrote in 1991: "the functional orthosis is an orthopaedic device which is designed to promote structural integrity of the joints of the foot and lower limb, by resisting ground reaction forces that cause abnormal skeletal motion to occur during the stance phase of gait" (Anthony, Raymond J.: The Manufacture and Use of the Functional Foot Orthosis. Karger, Basel, Switzerland, 1991, p. 5). In one of the more recently published reference books on podiatric biomechanics, Ray Anthony’s definition of a functional orthosis is also used as the working definition in a chapter on the materials used in foot orthoses (Olson, William R. "Orthotic Materials", in Valmassy, Ronald L. (ed), Clinical Biomechanics of the Lower Ext remity, Mosby, St. Louis, 1996, p. 308). Even though Anthony’s definition of a foot orthosis incorporates a relatively sophisticated description of how a foot orthosis functions, his definition can be further modified to make it even more currently accurate, given our present knowledge.
Last year I was involved in an e-mail discussion with other podiatrists from around the world in a forum called the Podiatry Mailbase, which is an electronic discussion list based in the United Kingdom (for more on the Podiatry Mailbase, go to the webpage at http://www.mailbase.ac.uk/lists-p-t/podiatry/). In this electronic discussion forum, those of us discussing the topic of definitions for foot orthoses came to the consensus that there was disagreement as to what would be the best definition of a foot orthosis especially given our current state of knowledge regarding the biomechanics of the foot and lower extremity.
At the time of my research of a good definition for foot orthoses, I was somewhat surprised to find that the definitions offered by Wu and Anthony seemed to be the only ones that I could find. Because of this relative lack of definitions for this very important subject, I offered the following definition of a foot orthosis on the Podiatry Mailbase which, I believe, still best reflects our current knowledge.
Definition of a Foot Orthosis: A foot orthosis is an in-shoe medical device which is designed to alter the magnitudes and temporal patterns of the reaction forces acting on the plantar aspect of the foot in order to allow more normal foot and lower extremity function and to decrease pathologic loading forces on the structural components of the foot and lower extremity during weightbearing activities. (K. Kirby, 1/7/98)
Since foot orthoses come in many types with different intended functions, it is important that podiatrists also have currently accurate definitions of the many subtypes of foot orthoses. Therefore, using the basic definition of a foot orthosis above, foot orthoses can also be subdivided into two main types, prescription foot orthoses and non-prescription foot orthoses, with definitions provided below.
Prescription foot orthoses are foot orthoses which are fabricated utilizing a three dimensional representation of the plantar foot and are specifically constructed for an individual using both weightbearing and nonweightbearing measurement parameters and using the observation of the foot and lower extremity functioning during weightbearing activities.
Non-prescription foot orthoses are foot orthoses which are fabricated in average sizes and shapes in an attempt to match the most prevalent sizes and shapes of feet within the population without utilizing a three dimensional representation of the plantar foot of the individual receiving the orthosis.
Depending on their intended purpose, prescription foot orthoses can also be further subdivided into three main types, functional foot orthoses, accommodative foot orthoses, and functional/accommodative foot orthoses.
Functional foot orthoses are prescription foot orthoses which are designed with the intent to alter the function of the joints of the foot and lower extremity during weightbearing activities.
Accommodative foot orthoses are prescription foot orthoses which are designed with the intent to alter the magnitude and temporal loading patterns of symptomatic or injured plantar structures of the foot during weightbearing activities.
Functional/accommodative foot orthoses are prescription foot orthoses which are designed both with the intent to alter the function of the joints of the foot and lower extremity and to alter the magnitude and temporal loading patterns of symptomatic or injured plantar structures of the foot during weightbearing activities.
REFERENCE: Dr. Kevin Kirby