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Introduction

What is an orthotic? An orthotic is a device used to mechanically assist, restrict, or control function of the musculoskeletal system [1]. Orthotics come in many shapes and sizes for different parts of the body, whether it be a leg prosthesis used by an amputee or a back brace used by someone with severe scoliosis. A foot orthotic is defined as a mechanical intermediary between the foot and the shoe [1]. Shoes are worn by the majority of our population as a protectant of the feet and specific shoe types can serve to enhance activities including running, hiking, jumping, dancing, etc.

Singularly, the word is orthotic. To pluralize the term, some simply add an 's' to result in orthotics; others, particularly those in the academic community, prefer the word orthoses.

Types of Foot Orthoses

What are the different types of foot orthotics (orthoses) and why do they work? There are three basic types of foot orthotics (orthoses): protective insoles, accommodative orthoses and functional orthoses.

Protective Insoles: Protective insoles supplement the soft tissue of the foot. Some of these devices are materials designed to provide shock absorption, while others are designed solely to provide supplemental cushion. As people age, the fat pad of the foot breaks down, often resulting in the sensation of 'walking on bone'. A cushion insole can protect the painful areas of the foot during ambulation (walking / running) and prevent long-term skin breakdown. Protective insoles can be purchased over-the-counter as 'ready to use' or they can be custom fitted in the podiatrist's office, where accommodations are added to a prefabricated insole to improve the fit of the device to the patient's foot.

Accommodative Orthoses: Accommodative orthoses adapt or 'accommodate' to the foot structure. The materials used in construction of the device determine whether the device provides support, cushion, protection or a mixture of the three. These materials have various qualities such as shock absorption, memory (prevents material from deforming under the patient's body weight), thermogenicity (ability to maintain heat or to disperse heat), and conformation (how well the material conforms to the foot).

Accommodative devices, like protective insoles, can be purchased over-the-counter as 'ready to wear', they can be custom fitted in the podiatrist's office, or they can be custom made. Custom made devices are usually manufactured from a plaster cast of the foot or directly molded to the foot by methods such as 'thermolding' wherein the orthotic is shaped to the foot after the material is heated to improve its malleability. Accommodative devices are often used in the treatment of diabetic ulcers, rheumatoid arthritis, neuropathy (loss of sensation), and peripheral vascular disease.

Functional Orthoses: Functional orthoses attempt to control the motion of the foot, either to prevent excess motion or provide motion. Merton Root, an expert in the field of biomechanics, states the purpose of the functional orthotic is to assist in controlling foot geometry and force directions by reducing the need for muscles to compensate or joints not staying in their more stable positions' [2]. When a joint does not function in its more stable position and muscles are made to compensate, pain results, whether immediately (acutely) or over the long term (chronically). Well-known examples of these painful results include tendonitis, arthritis, bone spurs, shin splits, and muscle spasms [3].

There are many types of functional orthotic devices, several bearing the name of the designer. These devices are usually custom made from a plaster cast of the foot taken in the podiatrist's office. The extensive steps in the fabrication of these devices contribute to the total expense. Functional orthoses are often used in the treatment of mechanical imbalances, foot deformities caused by cerebral palsy or other neurological conditions, pronation syndrome (excessive flattening of the arch), hallux limitus (limited motion at the big toe), plantar fasciitis (heel spur syndrome), and hallux abducto-valgus (bunion deformity). Specialized functional devices devices can be constructed to counteract marked pronatory forces encountered in running (Blake device) or to provide accommodative along with functional control in specific sport conditions. Devices can be custom made for the ballet dancer who is en pointe or for the runner who has been diagnosed with over-pronation or pronation syndrome.

How to Use Foot Orthoses

How does one use orthotic devices? Whether you have had plaster casts made of your feet and have just been handed a pair of custom made orthoses by your podiatrist or you have just been to the local drug store or sports store and now have an 'over-the-counter' (OTC) pair of orthoses, these recommendations will benefit you. Any type of shoe insert or orthotic must be gradually 'broken-in'. This means that the wearer (that's you) must get used to wearing the device in the shoe over time. For some people, this means a few days. For others, this means a couple of months. In general, functional orthotic devices take more time to 'break-in' than the accommodative devices. Remember that the functional orthotic is attempting to control or change the way the foot functions. The accommodative device is providing padding, cushion and / or shock absorption. Most podiatrists recommend that the orthotic be worn for one hour the first day, two hours the second day, etc., increasing the wear time until the device can be worn for a full day without discomfort.

Any insert or orthotic device placed in the shoe affects the way the foot functions, thus affecting the joints proximal to (above) the foot. Those joints include the ankle, the knee, the hip, the back and the neck, in general. If at any time knee pain, hip pain or back pain occur, the devices should be removed from the shoes for the remainder of the day, then re-inserted in the shoes the following day. Should this cycle of pain continue for over a week, contact your podiatrist for reevaluation.

When attempting to purchase shoes to wear with foot orthoses, the orthotic devices should be tried on with the shoes prior to purchase. The heel cup of the shoe must be relatively deep in order to accommodate the orthotic device. If the heel cup is too shallow, the heel will slip out of the shoe during ambulation. Most athletic shoes will accommodate orthotic devices easily. Some prefer to remove the insole that comes with the shoe; others prefer to wear the orthotic under the insole, while others prefer to wear the orthotic on top of the insole. Most styles of men's dress shoes will accommodate orthotic devices, as long as the heel cup is not too shallow. Women usually have to go with a 'boxier' or 'chunkier' type of dress shoe to accommodate the orthotic device. A specialized dress orthotic can be custom-made to fit into dress pumps or high heels.

Cost

Orthoses range in price from $20-40 for over-the-counter devices and $300-400 for custom-molded devices. Over-the-counter devices are less durable and may not support your foot in the most ideal position. Some doctors will try over-the-counter orthoses first to gauge the effectiveness of the device before asking you to part with hundreds of dollars for a pair custom molded to your feet.

Conclusion

This overview of foot orthoses has merely scratched the surface of the topic. Foot orthotics (orthoses) are purposed to aid in one's gait or ambulation (walking / running). There are many types of orthotic devices for many different foot conditions. A qualified podiatrist is able to assess the foot clinically, determining if the need exists for an orthotic device and what type of device will best meet that need.

References

1. McGuire, JB: ACFAOM Review Text in Podiatric Orthopedics and Primary Podiatric Medicine. Data Trace Publishing, Maryland. p191, 1997
2. Root, Orien, Weed: Normal and Abnormal Function of the Foot. Clinical Biomechanics Corporation, California. p73, 1997.
3. Harkless, LB, et al: Foot and Ankle Secrets. Hanley & Belfus, Inc., Philadelphia. p114, 1998.
4. Pal, S: Heel Pain: What your patients do and don't know. Biomechanics: The Magazine of Body Movement and Medicine. July 1999.
5. Hunter, S: Foot Types: Are Foot Types Related to Injury? Biomechanics: The Magazine of Body Movement and Medicine. May 1997.

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