By definition, an orthosis is designed to support and align the lower extremity, prevent or correct deformities, substitute for function, and relieve pain. Despite the uniqueness of each patient, mechanically speaking, the general goals of orthotic therapy are the same for all.
Dysfunctional movement patterns must be discouraged; joints with ligamentous laxities must be realigned and stabilized; soft tissue contractures must be stretched; and muscle weakness must be controlled to provide a stable stance phase during periods of weight transfer. Each orthosis must realign mechanical levers of the forefoot and hindfoot in all three planes of motion to provide a stable base of support. While its goal is to improve foot function, which is what every orthosis aims for, a foot orthosis can only achieve its goal in conjunction with a shoe.
Types of Foot Orthosis Available
A foot orthosis works to compensate for factors that lessen the foot’s ability to function normally through control of the dysfunction. There are basically three types of foot orthosis available: off-the-shelf, custom-fitted, and custom-made.
- Off-the-shelf orthotic products are available in pharmacies, supermarkets, and shoe stores. Off-the-shelf orthoses are mass produced for general use and the effectiveness of these foot orthoses will depend on the material and its ability to control the dysfunction. These orthoses are generally used for support of simple foot fatigue or for use in fashionable shoes that will not accommodate more structured foot orthosis. These items, for the most part, can not be modified to accommodate the variations that occur in both feet.
- Custom-fitted foot orthoses are mass produced of materials and design that can be easily modified to the individual’s personal needs. These foot orthoses are more structured in nature and are to be used when the patient is experiencing more discomfort or when the level of activities is such that off- the-shelf orthoses can’t control the problem(s).
- Custom-made foot orthoses are designed to accommodate each particular foot and individual foot dysfunction. Since the more chronic foot deformities seem to vary between the two feet, a more accurate design through a casting of the feet will be necessary. As for the type of foot orthosis and material used, this will be determined by the diagnosis and the degree of control required to correct or stabilize the dysfunction. Due to the severity of these dysfunctions, off-the-shelf and custom-fitted foot orthoses generally do not relieve the patient of sufficient discomfort.
Consult with your Pedorthist
for proper application of your condition.
Material of the Foot Orthosis
To support and align the lower extremity, to prevent or correct deformities: the essence of the foot orthosis is to control the foot dysfunction. Here is where material becomes the basis for success. Orthotic materials are chosen based on the individual’s foot structure, current levels of activity, age, and physical condition. Because those factors will change, so will the person’s orthotic needs. The more common materials available are (ridged) plastic, (semi-ridged) cork, and (soft) Pe-lite or crepe. Durability of materials is a consideration in orthosis fabrication because the orthotic must remain strong enough to do its job. The lifespan of the orthosis should be measured not by when it wears out but by how long it meets the foot’s changing needs.
Why Does a Foot Orthosis Depend on the Shoe?
As we know, foot orthoses are designed to control the biomechanical weakness of the lower extremity and to provide a stable stance phase during periods of weight transfer. The success of the foot orthosis to achieve its goal relies on the foundation, called the shoe, that the foot orthosis rest on. To maximize the efficiency of the foot orthosis, the shoe must meet the following requirements:
- Proper fit to the foot and its shape with foot orthosis in the shoe.
- As wide of a base or sole as that of the foot orthosis.
- Firm heel counter extended as far forwards on both sides as possible.
- Firm sole to insure a natural contact with ground causing minimal rolling.
- Ample room inside of shoe to allow the foot orthosis to lay flat inside of the shoe.
- Tie shoe in order to gain as snug a fit as possible over the instep and around the heel.
- In some cases, extra depth in the toe area.
An Effective Orthosis
Fits the Foot and the Shoe.
Once the orthosis has been fitted, a gradual break-in period allows the patient to acclimate to the pressure within the orthosis as the limb is realigned and stabilized. During this time, the patient is asked to vary the use of the orthosis a few hours a day, increasing each day until wearing full-time. Full-time wear will vary by patient, but most can expect consistent wear within two weeks.
Follow-up visits will be used to adjust the foot orthosis in order to alleviate any discomfort and improve foot function. Modifications are an integral part of the success of the foot orthosis in managing the foot discomfort.
What Makes a Foot Orthosis Fail?
- Inability to control navicular drop:
The ability of a device to contour precisely to an individual’s arch is very important in increasing the efficiency of biomechanical control of the device.
- Poor selection of materials:
Even when arch contour is precisely maintained, improper selection of materials used to construct the orthosis may allow excessive deformation of the device and thereby fail to limit abnormal foot motion.
- Poor stabilization of the heel:
For an orthotic device to perform properly, it must be able to cup or surround the calcaneus (heel bone), preventing it from rolling excessively either medially or laterally (side to side).
- Improper footwear:
Poor structure of footwear, inadequate fit of the foot orthosis to the shoe, and improper contour of footwear to the shape of the foot will create an inefficiency of the foot orthosis to perform its prescribed purpose.