Effects of inferior tibiofibular syndesmosis injury and screw stabilization on motion of the ankle: a finite element study.

PURPOSE: Traditional studies of syndesmosis injury and screw stabilization have been conducted in cadaveric models, which cannot yield sufficient and exact biomechanical data about the interior of the ankle. The purpose of this study was to evaluate the effects of inferior tibiofibular syndesmosis injury (ITSI) and screw stabilization on the motion of the ankle with finite element analysis.

METHODS: Three-dimensional models of the ankle complex were created with CT images of a volunteer's right ankle in three states: normal, post-ITSI, and stabilization with a screw 2.5 cm above (parallel to) the ankle. Simulated loads were applied under three conditions: neutral position with single foot standing, internal rotation, and external rotation of the ankle.

RESULTS: Compared with the normal state, ITSI increased the relative displacement between the lower extremes of the tibia and fibula in the anteroposterior and mediolateral directions and the angular motion of the tibia, fibula, and talus at internal and external rotations (ERs). However, when stabilized with syndesmotic screws, the range of motion (ROM) and all these parameters significantly decreased.

CONCLUSION: ITSI can lead to internal and ER instability of the ankle joint. Screw stabilization is effective in controlling the instability, but may reduce markedly the ROM of the ankle joint. Through this study, it can be proposed that the screws should be removed once the healing is gained in order to restore normal function of the ankle joint as soon as possible.