Neurosurgery Resident University of Maryland Medical Center Baltimore, MD, US
Disclosure(s):
Kevin T. Kim, MD: No financial relationships to disclose
Introduction: Sacroiliac joint dysfunction is increasingly recognized as a cause of lower back pain. Predicting SIJ dysfunction after lumbosacral fusion remains a difficult task for spine surgeons. No study has examined the association of spinopelvic parameters with the need for SIJ fusion after lumbosacral fusion.
Methods: We performed a retrospective analysis of patients who underwent spinal fusion surgery between 2016-2022. Patients with fusion including S1 and patients with fusion to S1 plus iliac fixation were included. Patients with < 2-year follow-up data, lower instrumented vertebra (LIV) L5 or higher, lack of adequate post-operative standing radiographs, S2-alar-iliac pelvic fixation technique, and sacroiliac joint dysfunction at the time of the surgery were excluded. Demographics and surgical variables were collected. Spinopelvic parameters were measured on standing radiographs. Summary statistics, univariate, and multivariable analyses were performed.
Results: Ninety-two patients were identified for this study. Mean age was 61.40 +/- 10.77 years. Sex was female in 62%. Mean BMI was 30.87 +/- 6.79. There were 50 (54.3%) patients with instrumentation to S1 and 42 (45.7%) patients instrumentation to the ilium. Among the entire cohort, 32 (34.8%) had positive response to post-operative sacroiliac joint injections and 25 (27.2%) underwent sacroiliac joint fusion after positive injections. Head-to-head comparison of patients that did and did not have sacroiliac joint fusion after spinal fusion showed that there were no significant differences in age, BMI, smoking status, bone radiodensity (mean HU at S1), number of spinal fusion levels, iliac fixation, interbody technique at L5-S1, or post-operative pelvic incidence (PI), lumbar lordosis (LL), and sacral slope (SS). There was no difference in sacroiliac joint fusion between fusion to S1 only and fusion to S1 plus iliac fixation. More patients undergoing sacroiliac joint fusion were female (p=0.029), had higher post-operative pelvic tilt (p < 0.001) and higher post-operative PI-LL mismatch (p=0.003). On multivariable analysis by the Jeffreys prior after forward selection, higher post-operative PT [OR 1.101, LL 1.034, UL 1.182, p=0.002] was an independent and significant predictor for need for sacroiliac joint fusion.
Conclusion : Patients with higher post-operative pelvic tilt more likely to develop sacroiliac joint dysfunction and have sacroiliac joint fusion after lumbosacral fusion surgery.