An In Vitro Biomechanical Analysis of Contralateral Sacroiliac Joint Motion Following Unilateral Sacroiliac Stabilization with and without Lumbosacral Fixation

ABSTRACT

Methods@#Seven human lumbopelvic spines were used, each affixed to six-degrees-of-freedom testing apparatus; 8.5-Nm pure unconstrained bending moments applied in flexion-extension, lateral bending, and axial rotation. The ROM of left and right SIJ was measured using a motion analysis system. Each specimen tested as (1) intact, (2) injury (left), (3) L5–S1 fixation, (4) unilateral stabilization (left), (5) unilateral stabilization+L5–S1 fixation, (6) bilateral stabilization, and (7) bilateral stabilization+L5–S1 fixation. Both left-sided iliosacral and posterior ligaments were cut for injury condition to model SIJ instability before surgery. @*Results@#There were no statistical differences between fixated and contralateral nonfixated SIJ ROM following unilateral stabilization with/without L5–S1 fixation for all loading directions (p>0.930). Injured condition and L5–S1 fixation provided the largest motion increases across both joints; no significant differences were recorded between SIJs in any loading direction (p>0.850). Unilateral and bilateral stabilization with/without L5–S1 fixation reduced ROM compared with the injured condition for both SIJs, with bilateral stabilization providing maximum stability. @*Conclusions@#In the cadaveric model, unilateral SIJ stabilization with/without lumbosacral fixation did not lead to significant contralateral SIJ hypermobility; long-term changes and in vivo response may differ.