Mark A. Matey, D.P.M. and Stephen M. Meritt, D.P.M. are Podiatrists in private practice at Methodist Medical Center.

Custom orthotic devices are classically used for common maladies of the foot. There are two basic types of orthotics: accommodative and functional. Accommodative orthotics are used to distribute the patient's body weight away from a painful area. The role of functional orthotics is to prevent pain during ambulation and more importantly to prevent pathologic range of motion in the joints of the foot. The functional orthotic is casted to the foot in a corrected position and sent to a laboratory where a hard plastic is used to make the device. 
The development of new, lighter, stronger, materials has increased the variety of devices and computerization has improved the overall quality of these products. When the foot is subjected to persistent abnormal patterns of gait, a particular set of symptoms will follow. The principles of biomechanics in the lower extremity must be understood before attempting to prescribe these devices. Human gait has been described by Steindler as " a series of movements where the body moves forward and the legs are placed in front of the trunk to prevent us from falling on our faces1." This point is clearly demonstrated by watching babies take their first steps with arms flailing, body swaying from side to side, and finally falling into mommy or daddy's outstretched arms. This explanation is misleading as to the simplicity of the process. There are 26 bones in the foot alone with 17 functional joints and many more articulations. There are numerous intrinsic and extrinsic muscles of the foot innervated by 6 nerves acting on those joints. In addition, there are precise applications of all the lower extremity and postural muscles. Therefore, each has a specific function and firing order in the sequence of movements that make up gait. Therefore the act of walking must be a well coordinated psychoneural and musculoskeletal process that is both repeatable step after step and accommodates to changes in conditions1. There are many variations of this pathway that may be considered ambulation but not necessarily normal gait. Variants to normal gait can be due to congenital anomaly, anatomic variation and loss of function due to traumatic event. It is when these variants of normal gait are multiplied by years of walking that most foot pathology occurs. Each year of walking consists of over 2.5 million steps and each walking step translates to a force of 2.5 times our body weight.

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