Radiographic analysis of hallux valgus. A two-dimensional coordinate system.

A new method was devised for the evaluation of medial and lateral splaying of the foot on dorsoplantar radiographs made while the patient is bearing weight. This method involves use of a two-dimensional coordinate system; the axis of the shaft of the second metatarsal is the x axis, the intersection of the x axis with the proximal end of the second metatarsal is the point of origin, and the perpendicular to the x axis that passes through the point of origin is the y axis. This method was used to study the radiographs of 177 feet of 112 female patients who had symptomatic hallux valgus and those of ninety-four normal feet of sixty-four female subjects. The site of origin of metatarsus primus varus in the patients who had hallux valgus was the first metatarsocuneiform joint. The great toe and first metatarsal of the patients who had hallux valgus were longer, on the average, than those of the normal subjects. However, the x coordinates at the tip of the great toe and at the end of the first metatarsal were larger only in the patients who were less than twenty years old, because of the progression of angulation of the great toe and of the first metatarsal in the older patients.