Mechanical Stress Redistribution in the First Metatarsal Bone After Autologous Bone Harvesting.

Abstract

The first metatarsal bone is a viable source for autologous bone grafting in foot and ankle surgery and may serve as another convenient graft site to correct a flail toe deformity. We aimed to determine how progressive bone removal from the first metatarsal affects the mechanical redistribution of the foot and whether this bone removal increases the risk of fracture. A three-dimensional finite element model developed from computed tomographic images obtained from a healthy man were used to evaluate traction stresses on the first metatarsal bone as a function of applied loads on the talus and Achilles tendon at two phases of the gait cycle (and according to the depth of bone removal). Simulations indicated that when maximum load was applied to the Achilles tendon, tensile stress increased from 2.049 MPa in the intact foot to 5.941 MPa in the area of maximum bone harvest during the stance phase. Furthermore, as the volume of bone extracted from the first metatarsal increased, there was a redistribution of stress that differed significantly from that of the intact foot. Although the maximum stress on the first metatarsal was not significantly affected by increasing the volume of bone harvested, the ankle should be splinted in plantarflexion during the postoperative period to eliminate the stance phase of gait and reduce the risk of metatarsal fracture.