Biomechanical Research On An Elastic Internal Fixation Bolt For Treating Distal Lower Extremity Syndesmosis Injury

Purpose: The goal of this study was to explore the effect of biomechanical property on an elastic internal fixation bolt fixing for distal lower extremity syndesmosis injury and to understand the superiority of this internal fixation bolt. Methods: A total of 12 frozen calves from 6 male cadavers were cut anteroinferior tibiofibular ligament, posteroinferior tibiofibular ligament, transverse tibiofibular ligament, interosseous tibiofibular ligament and deltoid ligament to make syndesmosis injury models, and were randomly divided into two groups: the elastic bolt group and the conventional screw group. Separation displacement, foot and ankle's axial stiffness and inferior tibiofibular intra-articular pressure distribution of baseline, model, elastic bolt group and conventional screw group were measured by biomechanical testing methods, optical non-contact measurement system and stress measurement system. Results: Both elastic bolt and conventional screw could preferably control the separation displacement of syndesmosis injury but conventional screw was stronger than bolt. The axial stiffness of foot and ankle after bolt and screw fixation showed a strong resistance ability to deformation, for which bolt was weaker than screw fixation. Additionally, pressure concentration distribution had some lateral shift for both elastic bolt and conventional screw group, and the former one had less shift which was similar to the intra-articular pressure concentration distribution of a healthy tibiofibular joint. Conclusion: The elastic fixation bolt device for the treatment of syndesmosis injury can maintain the inferior tibiofibular joint micromotion, achieve normal biomechanical characteristics of tibiofibular joint and promote the rehabilitation of syndesmosis injuries.