Summary

We use a three-dimensional finite element method to investigate how intramedullary screws disperse localized stress at the lateral cortex of the 5th metatarsal. Intramedullary screw fixation in Jones fractures contributes to dispersal of localized stress and aids in preventing refracture, to a certain extent.

Abstract

The Jones fracture is a proximal junctional metaphyseal/diaphyseal fracture of the fifth metatarsal, and is difficult to treat because of the risk of refracture and delayed union. Since intramedullary screw fixation has been described, the result of treatment has improved. However, refracture of Jones fractures after intramedullary screw fixation remains an issue. The purpose of this study is to clarify how much surgical treatment for Jones fracture could contribute to prevent refracture. We use a three-dimensional finite element method to investigate how intramedullary screws disperse localized stress at the lateral cortex of the 5th metatarsal. ?Methods?We used Acutrak 4/5 screw for intramedullary screw fixation for a 25 years old soccer player with Jones fracture. Before and after operation, a CT scan was performed to produce the 3D finite element model. Imaginary force to make Jones fracture was introduced gradually to the model. ?Results?Before operation, application of 1320N resulted in a crack at the lateral cortex, and a complete Jones fracture was found at 1600N. After operation, tensile stress occurred at the lateral side of the screw over 840N. Until 1400N, minimal effect was found at the lateral cortex of the 5th metatarsal. However, with imaginary force increase, a crack was seen at the site of Jones fracture at 1500N, and complete fracture extended to the screw at 1700N.?Conclusions?Intramedullary screw fixation in Jones fractures contributes to dispersal of localized stress and aids in preventing refracture, to a certain extent.