Medial arch strain after lateral column lengthening: an in vitro study

Posterior tibial tendon dysfunction with concomitant progressive flatfoot deformity is associated with ligamentous failure along the medial arch. Lateral column lengthening is being used alone and in combination with other procedures with the expectation that it contributes to restoring and maintaining the arch. The primary objective of this study was to examine the effect of lateral column lengthening on medial arch strain. A secondary objective was to examine the effect of subtalar, talonavicular, double and triple fusions on medial arch strain. Whole cadaver feet were subjected to vertical loads while in a plantigrade position. Spring ligament length was monitored using liquid metal displacement gauges. Two outcomes were examined: the length of the ligament and the change in length of the ligament per unit of applied load. Ligament length was unchanged after lateral column lengthening. Ligament length was decreased after talonavicular, double and triple arthrodeses, consistent with the ligament being protected by these fusions. The change in length per unit of applied load after simulated lateral column lengthening was comparable to that for the intact foot, which is consistent with the ligament remaining functional during weightbearing and not being overloaded.