Medial arch strain after medial displacement calcaneal osteotomy: an in vitro study.

Posterior tibial tendon dysfunction with concomitant progressive flatfoot deformity is associated with ligamentous failure along the medial arch. Medial displacement calcaneal osteotomy is being used alone and in combination with other procedures, with the expectation that it contributes to maintaining the arch. The objective of this study was to examine the effect of osteotomy on reducing medial arch strain. Whole cadaver feet were subjected to vertical loads while plantigrade. Spring ligament length was monitored using liquid metal displacement gauges. Two outcomes were examined: the length of the ligament under one-half body weight and the change in length of the ligament per unit of applied load. The medial displacement calcaneal osteotomy allowed elongation of the ligament with weightbearing, but at a shorter ligament length. This afforded the spring ligament protection from the levels of force experienced in the intact and lateral column-lengthened conditions.