Mathematical analysis of first metatarsal osteotomies.

The mathematical analysis of most first metatarsal osteotomy corrections for metatarsus primus varus is presented and interpreted with respect to metatarsal lengthening or shortening and changes in clinical reference angles (e.g., intermetatarsal or angle of declination). The critical parameters for each osteotomy such as location and angles of cuts and amount of displacement are defined and their theoretical effects on the final correction determined. Although exactitude in surgical methodology and an absolute prediction of final clinical results are impossible at the present time, even guidelines as to the potential effectiveness of various surgical techniques and quantitative methods for subsequent evaluation are lacking. This mathematical analysis can provide guidelines for prospective choices and a basis for retrospective interpretation as well as represent a critical component for biomechanical calculations.