The effect of proximal tibiofibular joint dislocation on knee mechanics: reduction and fixation matters

Purpose Proximal tibiofibular joint (PTFJ) dislocations are under-investigated injuries. There is scant basic science or clinical evidence to direct management. The purpose of this study was twofold; first to investigate the pathomechanics of PTFJ dislocation on knee mechanics. The second purpose was to evaluate knee mechanics following reduction and fixation. Methods Six cadaveric legs were tested on a mechanical platform. A 5 Nm external rotation force was applied to each knee and the external rotation and fibular translation was measured for several study conditions at 0 degrees, 30 degrees, and 90 degrees of flexion. Conditions included: the native state, transection of the posterior PTFJ ligament, transection of the anterior and posterior ligaments, screw fixation, and suspensory fixation. Screw fixation was performed using a single quadricortical 3.5 mm screw. Suspensory fixation was performed using an Arthrex TightRope device Results Transection of the anterior and posterior ligaments increased external rotation by 4.3 degrees, 5.9 degrees, and 5.6 degrees, at 0 degrees, 30 degrees, and 90 degrees (p <= 0.001), respectively. Screw and suspensory fixation returned external rotation to a near native state with mild overconstraint. Complete transection of anterior and posterior ligaments resulted in pathologic anterior fibular translation of 1.51 mm (p = 0.001), 1 mm, (p = 0.02) and 0.44 mm (p = 0.69) for 0 degrees, 30 degrees, 90 degrees of knee flexion. Screw and suspensory fixation restored native translation at all points with a small degree of overconstraint. Conclusion Disruption of the PTFJ causes pathologic external rotation and anterior fibular translation. Fixation restores near native motion with minor overconstraint. Surgeons should consider reduction and fixation of PTFJ injuries to restore native knee mechanics.