Evaluation of a minimally invasive procedure for sacroiliac joint fusion – an in vitro biomechanical analysis of initial and cycled properties

INTRODUCTION Sacroiliac (SI) joint pain has become a recognized factor in low back pain. The purpose of this study was to investigate the effect of a minimally invasive surgical SI joint fusion procedure on the in vitro biomechanics of the SI joint before and after cyclic loading. METHODS SEVEN CADAVERIC SPECIMENS WERE TESTED UNDER THE FOLLOWING CONDITIONS: intact, posterior ligaments (PL) and pubic symphysis (PS) cut, treated (three implants placed), and after 5,000 cycles of flexion-extension. The range of motion (ROM) in flexion-extension, lateral bending, and axial rotation was determined with an applied 7.5 N · m moment using an optoelectronic system. Results for each ROM were compared using a repeated measures analysis of variance (ANOVA) with a Holm-Šidák post-hoc test. RESULTS Placement of three fusion devices decreased the flexion-extension ROM. Lateral bending and axial rotation were not significantly altered. All PL/PS cut and post-cyclic ROMs were larger than in the intact condition. The 5,000 cycles of flexion-extension did not lead to a significant increase in any ROMs. DISCUSSION In the current model, placement of three 7.0 mm iFuse Implants significantly decreased the flexion-extension ROM. Joint ROM was not increased by 5,000 flexion-extension cycles.