Posterior Intra-articular Fixation Stabilizes Both Primary and Secondary Sacroiliac Joints: A Cadaveric Study and Comparison to Lateral Trans-articular Fixation Literature

Abstract

Abstract Background Posterior and lateral techniques have been described as approaches to sacroiliac joint arthrodesis. The purpose of this study was to compare the stabilizing effects of a novel posterior stabilization implant and technique to a previously published lateral approach in a cadaveric multidirectional bending model. We hypothesized that both approaches would have an equivalent stabilizing effect in flexion-extension, and that the posterior approach would exhibit better performance in lateral bending and axial rotation. We further hypothesized that unilateral and bilateral posterior fixation would stabilize both the primary and secondary joints. Methods Ranges of Motion (RoMs) of six cadaveric sacroiliac joints were evaluated by an optical tracking system, in a multidirectional flexibility pure moment model, between ± 7.5 Nm applied moment in flexion-extension, lateral bending, and axial rotation under intact, unilateral fixation, and bilateral fixation conditions. Results Intact RoMs were equivalent between both samples. Unilateral posterior intra-articular fixation reduced the RoMs of both primary and secondary joints in all loading planes (flexion-extension RoM by 45%, lateral bending RoM by 47%, and axial RoM by 33%), and bilateral fixation maintained this stabilizing effect in both joints (flexion-extension at 48%, in lateral bending at 53%, and in axial rotation at 42%). Only bilateral lateral trans-articular fixation reduced mean RoM of both primary and secondary sacroiliac joints, and only under flexion-extension loads (60%). Conclusion During flexion-extension, the posterior approach is equivalent to the lateral approach; while producing superior stabilization during lateral bend, and axial rotation.