Evaluation of Fusion and Patient Outcome After Minimally Invasive Sacroiliac Joint Fusion Surgery with Decortication: 12-month Results

Presented at SMISS Annual Forum 2016
By William Cross MD
With Arnold Delbridge MD, Donald Hales MD,

Disclosures: William Cross MD None Arnold Delbridge MD None, Donald Hales MD B; Zyga Tech.,


The sacroiliac (SI) joint is the source of pain in approximately 18% of chronic low back pain cases. After conservative treatment options are exhausted, patients may be indicated for minimally invasive surgical fusion of the joint. Time-to-fusion for the SI joint is not well reported. Previous literature examined SI joint fusion post-surgery at 5 years and a separate trial demonstrated only a small percentage of SI joints fuse within 1 year.


The purpose of this study was to evaluate radiological evidence of arthrodesis and patient pain score reduction post SI joint fusion with decortication at 12 and 24 months. 


This prospective, multi-center study enrolled patients previously receiving SI joint fusion with decortication (SImmetry) prior to their 12-month visit. Thin-slice computerized tomography (CT) was collected and submitted to an independent core laboratory (Medical Metrics, Inc.) for evaluation. Non-biased radiologists experienced in evaluating the SI joint independently reviewed all CTs for fusion in relation to the joint and the area of decortication. Fusion was defined as presence of a continuous segment of solid bridging bone that extends from sacrum to ilium. Pain quantified by numeric pain scale and adverse events were also reported. 


19 patients at three institutions were enrolled and completed a 12-month visit and CT. All patients received SIJ fixation with threaded implant(s) after undergoing decortication and bone graft insertion. At 12 months, fusion was reported in 74% (14/19) of patients. Of the 14 fused patients, 12/14 had fusion within the area of joint decortication. Smoking status and age did not appear to affect fusion (p = 0.6967 and p = 0.4423, respectively). Back pain severity decreased from 7.5 to 2.5 on a 10-point scale (reduction of 67%). Freedom from device- or procedure-related serious adverse events through 12 months was 100%. 


Minimally invasive SIJ fusion surgery can result in radiographically identifiable arthrodesis as early as 12 months. Decortication and bone grafting may contribute to earlier fusion than seen in other trials. In addition, minimally invasive SIJ fusion surgery with arthrodesis provides significant pain relief at 1-year post-operatively.