The effect of minimally invasive sacroiliac joint fusion compared with sham operation: study protocol of a prospective double-blinded multicenter randomized controlled trial.

Background and purpose - The sacroiliac joint is increasingly recognized as a cause of pain in 15-30% of patients with low back pain. Nonoperative management is not always successful and surgical treatment with fusion of the joint is increasingly recommended. According to the literature, minimally invasive fusion reduces pain and improves function compared with nonoperative treatment. It is, however, unclear to what extent the placebo effect influences these results. Patients and methods - The trial is designed as a prospective multi-center, double-blind, randomized shamsurgery controlled trial with 2 parallel groups. 60 patients with a suspected diagnosis of sacroiliac joint pain confirmed with sacroiliac joint injection are included according to the trial inclusion criteria. Patients are randomized with a 1:1 allocation into 2 groups of 30 patients each. The primary end-point is group difference in sacroiliac joint pain intensity on the operated side at 6 months postoperatively, measured by the Numeric Rating Scale. The main objective is to examine whether there is a difference in pain reduction between patients treated with a minimally invasive fusion of the sacroiliac joint compared with patients undergoing a sham operation. Results - Unblinding occurs after the completed 6-month follow-up. The primary analysis will be performed when all patients have completed 6 months' follow-up. Follow-ups are continued to at least 2 years postoperatively. Data from the different groups will be compared based on the "intention to treat" principle.