359 Sacroiliac Joint Fusion – A Shift Towards Variant Anatomy and Their Clinical Implications

Abstract

INTRODUCTION: Sacroiliac joint (SIJ) dysfunction is a common cause of low back pain, estimated to account for 14-22%. Currently, a limited amount is known about risk factors predicting surgical outcomes. Few studies have evaluated the prevalence of variant SIJ anatomy, while none have investigated this in the pathologic SIJ. Furthermore, the impact SIJ morphology on outcomes is unknown. METHODS: We performed a retrospective review of patients undergoing SIJ fusion at our institution between 2014 and 2021. Inclusion criteria included patients 18 years or older, diagnosed with SIJ dysfunction refractory to conservative management. Clinical and sociodemographic information was collected from chart review. Two separate study team members independently reviewed CT and MRI studies, categorizing anatomic subtypes based on Prassopoulos et. al’s classification system. Disagreement was resolved by consensus for the final data analysis. RESULTS: A total of 77 joints were instrumented across 67 patients. Postoperative VAS significantly improved from preoperative VAS of 2 (0-5) and 6.6 (5.5-8) respectively (p < .001). Interestingly, median percent improvement and interquartile range (IQR) for smokers was 77.8 (50-100) compared to 57.1 (14.3-83.3) for non-smokers (p = 0.04). There were significantly fewer normal SIJs than previously reported (p < 0.05). There were differences in outcomes between anatomic subtypes, though this failed to reach statistical significance. CONCLUSIONS: SIJ fusion leads to significant improvement in patients with refractory SIJ pathology. The distribution across anatomic joint subtypes is markedly different in the pathologic SIJ. There appears to be differences in clinical outcomes between these subtypes. Further research is needed to power these results. These changes may further understanding on SIJ dysfunction pathophysiology and prompt additional investigations into differences in clinical outcomes.