421 - 24-month Clinical Evaluation of Radiographic Fusion after Minimally In...

Oral Posters: MIS

Presented by: W. Cross - View Audio/Video Presentation (Members Only)


W. Cross(1), A. Delbridge(2), D. Hales(3)

(1) Mayo Clinic, Rochester, MN, United States
(2) Cedar Valley Medical Specialists, Waterloo, IA, United States
(3) Northern Arizona Orthopaedics, Flagstaff, AZ, United States


Background: The sacroiliac (SI) joint is increasingly recognized as a common source of low back pain, affecting as many as 15-30% of chronic low back pain cases. Conservative techniques such as exercise, pharmacologic intervention and injections provide relief for many. But after conservative treatment options are exhausted, patients may be indicated for SI joint arthrodesis. In recent years, clinical outcomes have improved with the advent of minimally invasive SI joint fusion procedures with mechanical fixation devices. Recent publications of clinical outcomes have focused on fixation of the SI joint rather than fusion; as such radiographic evidence of SI joint fusion and its timing post SI joint fusion surgery is limited. The purpose of this study was to evaluate radiological evidence of arthrodesis post SI joint fusion with decortication through 24 months.

Methods: A prospective, multi-center trial was conducted to evaluate radiographic evidence of fusion after minimally invasive SI joint fusion surgery with joint decortication and bone graft. Thin-slice computerized tomography (CT) was collected at 12 and 24 months after surgery for analysis. An independent core laboratory (Medical Metrics, Inc.) composed of unbiased radiologists experienced in evaluating the SI joint independently reviewed all CTs. Fusion was defined as presence of a continuous segment of solid bridging bone extending from the sacrum to the ilium. Analyses included radiographic analyses location of fusion and comparative analyses to evaluate the effect of baseline demographics and clinical outcomes of pain reduction to fusion of the SI joint.

Results: 19 patients at three institutions had SI joint fusion surgery with decortication, bone graft material and implantation of threaded implant(s). 18 patients completed 24 months of follow-up. Independent radiographic analysis verified the presence of solid, continuous bone fusion in 74% (14/19) of patients at 12 months and 83% (15/18) of patients at 24 months. Of the patients fused at 24 months, 87% developed fusion within the area that was decorticated during the surgical procedure. Low back pain decreased from 7.9/10 pre-operatively to 2.1/10 at 24 months (73% reduction in average pain, P< 0.0001). Smoking status, age, gender, body mass index, or implanting site did not appear to affect fusion of the SI joint. Freedom from device- or procedure-related serious adverse events through 24 months was 100%.

Conclusions: Minimally invasive SIJ fusion surgery with decortication and bone graft material can result in arthrodesis as early as 12 months with continued positive clinical outcomes through 24 months. Decortication and bone grafting may contribute to earlier fusion than seen in other trials. Minimally invasive SIJ fusion surgery provides significant pain relief 2-years post-operatively.