Safety and 6-month effectiveness of minimally invasive sacroiliac joint fusion: a prospective study

Bradley S Duhon,¹ Daniel J Cher,² Kathryn D Wine,² Harry Lockstadt,³ Don Kovalsky,⁴ Cheng-Lun Soo⁵

On behalf of the SIFI Study Group

¹Neurosurgical and Spine Specialists, Parker, CO, ²SI-BONE, Inc, San Jose, CA, ³Bluegrass Orthopaedics and Hand Care, Lexington, KY, ⁴Orthopaedic Center of Southern Illinois, Mount Vernon, IL, ⁵Health Research Institute, Oklahoma City, OK, USA

Background: Sacroiliac (SI) joint pain is an often overlooked cause of low back pain. SI joint arthrodesis has been reported to relieve pain and improve quality of life in patients suffering from degeneration or disruption of the SI joint who have failed non-surgical care. We report herein early results of a multicenter prospective single-arm cohort of patients with SI joint degeneration or disruption who underwent minimally invasive fusion using the iFuse Implant System^®.
Methods: The safety cohort includes 94 subjects at 23 sites with chronic SI joint pain who met study eligibility criteria and underwent minimally invasive SI joint fusion with the iFuse Implant System^® between August 2012 and September 2013. Subjects underwent structured assessments preoperatively, immediately postoperatively, and at 1, 3, and 6 months postoperatively, including SI joint and back pain visual analog scale (VAS), Oswestry Disability Index (ODI), Short Form-36 (SF-36), and EuroQoL-5D (EQ-5D). Patient satisfaction with surgery was assessed at 6 months. The effectiveness cohort includes the 32 subjects who have had 6-month follow-up to date.
Results: Mean subject age was 51 years (n=94, safety cohort) and 66% of patients were women. Subjects were highly debilitated at baseline (mean VAS pain score 78, mean ODI score 54). Three implants were used in 80% of patients; two patients underwent staged bilateral implants. Twenty-three adverse events occurred within 1 month of surgery and 29 additional events occurred between 30 days and latest follow-up. Six adverse events were severe but none were device-related. Complete 6-month postoperative follow-up was available in 26 subjects. In the effectiveness cohort, mean (± standard deviation) SI joint pain improved from a baseline score of 76 (±16.2) to a 6-month score of 29.3 (±23.3, an improvement of 49 points, P<0.0001), mean ODI improved from 55.3 (±10.7) to 38.9 (±18.5, an improvement of 15.8 points, P<0.0001) and SF-36 PCS improved from 30.7 (±4.3) to 37.0 (±10.7, an improvement of 6.7 points, P=0.003). Ninety percent of subjects who were ambulatory at baseline regained full ambulation by month 6; median time to full ambulation was 30 days. Satisfaction with the procedure was high at 85%.
Conclusion: Minimally invasive SI joint fusion using the iFuse Implant System^® is safe. Mid-term follow-up indicates a high rate of improvement in pain and function with high rates of patient satisfaction.

Keywords: minimally invasive surgery, sacroiliac joint, sacroiliac joint arthrodesis, spine surgery, prospective clinical trial