Lateral Transiliac MIS SI Joint Fusion: 1-year Follow-up Results from the Prospective Multicenter STACI Trial

Introduction: Sacroiliac joint (SIJ) dysfunction accounts for 15-30% of persistent lower back pain. Minimally invasive SIJ fusion (SIJF) has become a standard treatment for chronic, recalcitrant SIJ pain. Lateral transiliac SIJF, using implants bridging the ilium and sacrum, is supported by strong evidence demonstrating early and sustained improvements in pain and function. Traditionally performed by spine surgeons, this procedure is increasingly performed by interventional pain management (IPM) physicians. We present one-year follow-up results from a prospective, multi-center, single-arm clinical trial evaluating lateral SIJF performed by IPM physicians using threaded titanium implants.

Methods: STACI (NCT05870488) is a two-year follow-up study conducted at 15 U.S. sites. Adults with a confirmed SIJ-related diagnosis using NASS criteria, refractory to non-operative care were screened for eligibility. Inclusion criteria include: SIJ NRS pain score ≥ 5/10, ODI score ≥ 30%; excluded are those with prior SIJF, severe non-SIJ back pain, fibromyalgia, interfering comorbidities, and patients with worker’s compensation. Follow-up visits were conducted at 1-, 3-, 6-, 12-, and 24-months post-surgery. The primary endpoint was change in SIJ pain from baseline to 6 months after treatment. Secondary endpoints included changes in function (Oswestry Disability Index), pain (NRS), quality of life (PROMIS-29), device or procedure-related adverse events, and evidence of fusion on a CT scan at 2 years.

Results: A total of 110 participants were enrolled and treated. Mean (SD) age at study entry was 64 (14) years, BMI was 29 (5), and 68% are female. At study entry, mean ODI and SIJ NRS scores were 52 (13) and 7.5 (1.4), respectively with a main duration of SIJP of 7 years. Operative time was 44 (16) minutes with mean blood loss of 13.7 (15.5) cc and no intraoperative adverse events. Reported perioperative adverse events include one surgical site infection at and one surgical site hematoma. The surgical site infection was treated with antibiotics and resolved without sequelae. The hematoma was drained shortly after the study procedure, without further complication. At 12-months, mean (SD) SIJ pain decreased 5.3 points (p < 0.001) from 7.6 (1.5) at baseline, to 2.3 (2.2). Mean (SD) ODI improved 28.1 points (p < 0.001) from 52.1 (13.7) at baseline, to 24.0 (17.2) at 12-months.

Conclusion: These findings demonstrate that lateral SIJF performed by IPM physicians is both safe and effective, producing substantial and clinically meaningful improvements in pain and function at one year follow-up. Furthermore, outcomes are favorable when compared to studies of SIJF reported by surgeons.