Objective: The hypothesis tested was that the increased load on the medial arch of the flat foot can be reduced through a medial displacement calcaneal osteotomy.
Design: A three-dimensional, biomechanical, multisegment model was used in conjunction with experimental data from the literature.
Background: Biomechanical models have been used to study the plantar fascia, medial arch height, subtalar motion and distribution of forces in the foot.
Methods: Responses of a normal foot, a flat foot and a flat foot with a medial displacement calcaneal osteotomy to an applied load of 683 Newtons were analyzed, and the distribution of support among the metatarsal heads and moment about various joints were computed.
Results: Compared to the normal foot, our flat foot model shifts the distribution of support from the lateral to the medial side, decreasing support provided by the fifth metatarsal from 11% to 1% of the total load, increasing support provided by the first metatarsal from 12% to 22% and increasing the moment about the talo-navicular joint from 20 to 28 Newton-meters. A ten millimeter medial displacement calcaneal osteotomy shifts support back toward the lateral side, with 11% provided by the fifth metatarsal and 13% by the first metatarsal. The moment at the talo-navicular joint decreases to eighteen Newton-meters.
Conclusion: Our analysis indicates that a ten millimeter medial displacement calcaneal osteotomy in a flat foot model decreases the load on the medial arch.