Pathomechanical metatarsal arc: radiographic evaluation of its geometric configuration.

A total nonlinear relationship among all five metatarsals is presented in this article. This relationship is an equation whose graph is a conic curve. The metatarsal arc is defined as a conic curve that has a unique numeric value, its eccentricity. Thus, each metatarsal arc variation has a unique eccentricity value, an axis location value, and a coefficient of variation value. It is assumed that many of these metatarsal arc variations are pathomechanical, and that an optimal arc exists. A small sample yielded numeric values that appear to be related to the degree of pathomechanical variation. Based on a small sample, clinical experience, and a numeric classification that is theoretically attractive, it is recommended that the surgeon plan each case of forefoot surgery so that these numeric values are given due consideration in the establishment of a geometric configuration for the metatarsal arc. To obtain these numeric values, the surgeon can learn to analyze the radiographs mathematically or submit them to someone who can.