Study of the metatarsal formula in patient with primary metatarsalgia.

OBJECTIVES

The aims of this study were (i) to ascertain the prevalence of different types of metatarsal formula among patients with primary metatarsalgia; (ii) to compare the variable of "shortening of the first metatarsal in relation to the second" (I/II) between the metatarsalgia and control groups; and (iii) to analyze the intra and interobserver concordance by means of Morton's transverse line method and Hardy and Clapham's arc method.

METHODS

A cross-sectional observational study was conducted on 56 patients by means of radiographs on their 112 ft, of which 56 were in the metatarsalgia group and 56 in the control group. The evaluations were done between December 2012 and June 2013. The measurements were made by three third-year orthopedics residents with prior training in the methods used, and a template was used.

RESULTS

There was no concordance between the two methods, as shown by Bland-Altman plots, although the intraclass correlation coefficients showed that the intra and interobserver reproducibility was high using the transverse line method (0.78 and 0.85) and moderate using the arc method (0.73 and 0.60). Comparison between the groups showed that there was a statistical difference (p ≤ 0.05) such that there was greater shortening of the first metatarsal (3.39 mm) in the control group than in the metatarsalgia group (2.14 mm). In the patients with primary metatarsalgia, the index minus metatarsal formula was more prevalent according to the transverse line method (62.5%) and the zero plus type according to the arc method (71.4%).

CONCLUSION

In the present study, it was observed that the metatarsal formula prevalences depended on the measurement method. In both groups, shortening of the first metatarsal predominated. There was no intra or interobserver concordance in either of the two proposed methods.