RADIOGRAPHIC ASSESSMENT OF THE 2ND METATARSAL - MEASURE OF FIRST RAY HYPERMOBILITY

Hypermobility of the first metatarsal cuneiform joint has been implica ted as a cause of the hallux valgus deformity. The objective definitio n of hypermobility at this joint, however, has not been clearly define d. We used a modified Coleman block test to accentuate motion at the f irst metatarsal cuneiform joint in order to measure physiologic limits of motion in vivo. This motion was compared with radiographic analysi s of the feet, which included the hallux valgus angle, intermetatarsaI angle, and medial cortical thickening at the midshaft of the second m etatarsal, This assessment was performed on 100 feet (50 right feet an d 50 left feet in 50 patients). The average intermetatarsal angle was 8.7 degrees (range, 4-14 degrees), the average hallux valgus angle was 11 degrees (range, 4 degrees of varus to 30 degrees of valgus), and t he average midshaft medial cortical thickness was 3.2 mm (range, 2.0-5 .5 mm). Pearson's correlation coefficient was calculated to compare th ese factors. The relationship between variables was found to be small (r less than or equal to 0.2). Motion was noted to occur in the normal foot at this joint and a range of normal values for medial cortical t hickness was identified.