Sacroiliac Joint Fusion-A Shift Toward Variant Anatomy and Clinical Implications

Objective: To investigate impact of patient factors and sacroiliac joint (SIJ) anatomical structure on SIJ fusion outcomes.

Methods: This single-center, retrospective, observational study evaluated patients diagnosed with SIJ dysfunction refractory to conservative measures who had available preoperative imaging of the sacrum and underwent SIJ fusion surgery. The impact of patient sociodemographics on pain improvement was assessed by Mann-Whitney U test. Differences in patient sociodemographics and outcome information between anatomical subtypes were assessed with χ² and Kruskal-Wallis tests. χ² test was used to compare joint anatomy distribution between studies analyzing SIJ variations.

Results: We included 77 total joints that underwent instrumentation. There were significant differences between the anatomical subtypes with female sex having significantly higher rates of non-normal joint anatomy. Younger age was significantly more common in bipartite/dysmorphic anatomy (53.9 years) than normal anatomy (70 years) (P < 0.05). There was a trend toward better outcomes in bipartite/dysmorphic and accessory variants, while semicircular defect and crescent variants trended toward worse outcomes. Nonnormal anatomy was significantly more frequent in our population than previous reports on nonpathological SIJ.

Conclusions: A pathological SIJ has a significantly higher prevalence of variant joint anatomy. There appears to be a trend toward differences in surgical outcomes based on SIJ anatomy. Future research with larger sample sizes is necessary to confirm these differences.