Subchondral bone changes following sacroiliac joint arthrodesis - a morpho-mechanical assessment of surgical treatment of the painful joint

Background: Sacroiliac joint arthrodesis is an ultima ratio treatment option for sacroiliac joint dysfunction. Fusion drastically reduces sacroiliac joint movement providing long-lasting pain-relief associated with tension-relief to the innervated sacroiliac joint structures involved in force closure. Objectives: To display the bone mineralization distribution patterns of the subchondral bone plate in 3 distinct regions (superior, anterior, and inferior) of the sacral and iliac counterparts of the sacroiliac joint pre-and post-sacroiliac joint arthrodesis and compare patterns of sacroiliac joint dysfunction post-sacroiliac joint fusion with sacroiliac joint dysfunction pre-arthrodesis patterns and those from healthy controls. Study Design: An observational study. Setting: The research took place at the University of Basel, Switzerland, where the specific image analysis program (Analyze, v7.4, Biomedical Imaging Resources, Mayo Foundation, Rochester, NY, USA) was made av ailable. Methods: Mineralization densitograms of 18 sacroiliac joint dysfunction patients pre-and post-sacroiliac joint arthrodesis (⥠6, ⥠12, and ⥠24 months post-surgery) were obtained using computed tomography osteoabsorptiometry. For each patient, pre-vs. post-surgery statistical comparisons were undertaken, using the Hounsfield unit values derived from the subchondral mineralization of superior, anterior, and inferior regions on the iliac and sacral auricular surfaces. Post-operative values were also compared to those from a healthy control cohort (n = 39). Results: In the pre-operative cohort at all 3 follow-up times, the superior iliac region showed significantly higher Hounsfield unit values than the corresponding sacral region (P < 0.01). Mineralization comparisons were similar for the sacrum and ilium in the anterior and inferior regions at all follow-up points (P > 0.5) with no surgery-related changes. Sacral density increased significantly in the post-operative state.