STUDY DESIGN: A retrospective analysis of prospectively collected registry data. OBJECTIVE: To examine the subsequent pattern of surgeries and outcome of sacroiliac joint fusions (SJF) in patients previously operated in the lumbar spine as well as those scheduled for primary SJF. SUMMARY OF BACKGROUND DATA: Patients with SI joint pain often have a history of previous back surgery, but it is unclear how often patients require back surgery after SI-joint fusion. METHODS: We obtained data from the national Swedish spine registry on all patients who underwent a SJF between 1998 and 2019 and identified previous and additional operations of any type after a SJF between 1998 and 2022. The EuroQol EQ VAS and the Oswestry disability index (ODI) were registered preoperatively and 1 year after the last undergone surgery. Satisfaction with treatment was assessed 1 year after surgery. RESULTS: Two hundred seventy-nine patients underwent SJF between 1998 and 2019. Ninety-five of 279 patients (34%) underwent primary SJF, and 184 of 279 patients (66%) underwent SJF after spine surgery. Forty-one of 95 patients (43%) underwent additional spine or SI-joint surgery after a primary SJF. The most common additional procedure was contralateral SJF (22 of 41
54%). The mean EQ-VAS change after primary SJF was 19 points (95% CI 12-26), whereas the corresponding value for SJF after previous lumbar spine surgery was 9 points (95% CI 2-16). The corresponding values for the mean ODI change were -14 points (95% CI -19 to -10) and -9 points (95% CI -14 to -4) respectively. Seventy-three percent (37 of 51) and 54% (34 of 63) were satisfied after SJF after primary versus secondary SJF. CONCLUSION: After primary SJF most additional surgeries are for contralateral symptoms and 9% required lumbar surgery after their SJF. Two-thirds of the patients with SJF have had their surgery after lumbar surgery.