This article pertains to the design, approach and use of the orthotic in the podiatric practice. The reader of this information will have a basic understanding of the use of these devices in treating biomechanical dysfunctions of the foot. The article is limited due to the complexity of this topic. One should take caution in the use of this information. The sole purpose of this article is an introductory presentation.

Although the orthotic can be refered to as an arch support, arch device, orthoses or brace, the proper term should remain as orthotic or orthoses. Numerous reasons exist for prescribing such a device to render a patient relief from a biomechanical deficiency that has caused them discomfort or pain. Because numerous causes exist, there are also numerous variations on the designs. The goal of the orthotic is to attempt to render pain relief to the patient.

Before beginning any discussion of the various orthotics that are prescribed, an overview of the various foot types is needed. To simplify this, the reader may keep in mind three types of feet: the high arch (pes cavus), the normal arch and the flat foot (pes planus). All three types of feet will be susceptible to problems associated to improper function or dysfunction of the foot.

Keep in mind that the foot has two fold functions. The foot is a rigid lever and a mobile adaptor during heel strike to forefoot load. The lateral column of the foot receives the ground reactive forces and must remain stabile. The lateral column includes the calcaneus, cuboid, and the fourth and fifth metatarsals. When weight is borne on these bones, the midtarsal joint (MTJ) should become locked into the proper position to render stability. Instability of the MTJ leads to many podiatric problems (heel pain, neuromas and hammertoe are just a few examples).

As the foot transfers weight from the lateral column to the medial column, a dynamic reception of the ground occurs. Therefore, the medial column of the foot (the talus, cunieforms and metatarsals one, two, and three and their digits) has the dynamic function of the foot. The dynamic function is also known as a mobile adaptor on uneven ground or terrain such as walking on a hillside. It has as well the ability to allow momentary collapse of the arch to absorb "shock" from the impact of walking or running. As the heel lifts, the arch will rise from its lowest point. And the foot has performed a mobile adaptor.

When the arch collapses or lowers, it is called pronation. When the arch rises, it is called supination. The motions are highly complex that dampens impact during the weight bearing component of the gait cycle. Bearing this in mind, the orthotic should NOT support the arch. The arch needs to raise and lower. In the extreme flat foot or pes planus, the arch does not move; this is a reason of many problems of the foot. The use of a functional orthotic stops the "excessive lowering" of the arch. Therefore, the arch is not truly supported. Thus, the orthotic is misnamed as an arch support.

The motion of the arch is directly dictated by the position and motion to the heel (calcaneus). This is accomplished at the subtalar joint. At a heel strike of the contact phase of the gait cycle, the heel is inverted. That is, the plantar (bottom) of the heel is pointed to the mid line of the body and remains this way during the loading of the forefoot. It then moves to an everted position where the plantar is pointed away from the midline of the body. This motion is called eversion. The opposite motion is called inversion. Eversion occurs during pronation and inversion occurs during supination.

A heel which is everted at heel strike does not allow proper motion of the arch and is referred to as a pronated foot (low arch) as in a pes planus. A heel which is too inverted at heel strike is known as a supinated foot as seen in pes cavus. This attitude of the heel and motion of subtalar joint thus affects the foot in its ability to be a rigid lever and a mobile adaptor the arch must "piston" to absorb the shock from ground reactive forces.

Furthermore, the forefoot must be parallel to the ground to equally bear weight. A forefoot varus is a foot that is inverted to the rear foot. The surface of metatarsal phalangeal joints 1-5 are elevated on the inside when the heel is rectus (neither supinated nor everted) and the subtalar joint is in neutral position with the midtarsal joint is maximally pronated (or locked). In a forefoot valgus, the opposite is true. The plantar surface of the first through the fifth MPJ is pointed away from the midline of the body when the heel is rectus, subtalar joint is neutral with the MTJ pronated fully. A forefoot varus is seen in a pes planus foot usually and a forefoot valgus is usually associated with a pes cavus. It would be of great benefit to reread the above to help understand that which has been written.

The design of the orthotic should take the above factors into consideration. The orthotic must allow the rearfoot to relate to the forefoot through "normal" function. That is why these devices are named functional orthotics. Typically this orthotic will be prescribed for heel pain. As an example, the shell of the orthotic may be rigid or semi-flexible. The more rigidity there is, the more stability there will be. The softer orthotic is less effective in handling the body weight and normal mechanics of the body. The control is in the posting of the rearfoot and forefoot.

An accommodating device is designed to allow abnormal pressures to be transferred to neighboring structures. For example, a hypermobile first metatarsal will not bear weight properly under the first MPJ. This will cause pressure under the second MPJ. The accommodating orthotic will have a depression under the second mpj to relieve the pressure under the second MPJ. If the patient presents some sesamoiditis, the accommodation is under the first MPJ.

The above two orthotics are only a sample of the various orthotics available. These are designed from a cast molding of the patients feet. The cost of the orthotics range from $300-$500. It is advisable that one keeps in mind that these devices may take up to five months before 100% relief is achieved. Also, keep in mind that they might now totally rid the complaint that the patient presented. A surgical option is a possible result should this occur.

Dr. Graham has been in private practice in Effingham since 1989 and is on staff at St. Anthony's Memorial Hospital and Effingham Ambulatory Surgical Treatment Center. He is Board Certified by the American Board of Podiatric Surgery and American Board of Podiatric Orthopaedics and Primary Podiatric Medicine. Dr. Graham is a Fellow of the American College of Foot and Ankle Surgeons, the American College of Foot and Ankle Orthopaedics and Medicine, and American Professional Wound Care Association. He is also a member of the American Podiatric Medical Association and the Illinois Podiatric Medical Association.

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