Abstract
Studies have reported the source of chronic lower back, buttock, groin, or lower extremity pain is from disorders of the sacroiliac (SI) joint in 10% to 26% of cases (1-4). Nevertheless, sacroiliac joint dysfunction is a controversial topic as there is no single clinical, imaging, or provocative test that definitively confirms the SI joint as a primary source of pain (4). In addition, the SI joint may be a referred site of pain, including from a degenerative disc at L5-S1, spinal stenosis, or osteoarthritis of the hip.

SI joint pathology may include degenerative and inflammatory arthritis, post-traumatic arthritis, post-partum instability, post-infectious arthritis, joint degeneration related to previous lumbar spinal fusion, joint damage from previous posterior iliac crest bone graft harvesting, and neoplastic processes (3). This policy is directed at minimally-invasive surgical (MIS) fusion of the sacroiliac (SI) joint for treatment of degenerative sacroilitis or sacroiliac disruption.

Traditionally, treatment begins with conservative management (e.g., physical therapy, activity modification and analgesic medication). Open SI joint fusion has long been another option, albeit sparingly used given the significant morbidity associated with the depth and anatomic location of the SI joint. Recent survey data show MIS-SI joint fusion displacing open SI joint fusion (5). MIS-SI joint fusion involves percutaneous insertion of a metallic device across the SIJ that is intended to fuse the joint rather than just stabilize the joint as with simple of insertion of screws. Smith reported a retrospective multi-center comparison of MIS-SI joint fusion with open SI joint fusion in 114 and 149 patients, respectively (6), with MIS-SI joint fusion demonstrating statistically positive outcomes. Though both groups seemed to improve, there was reportedly an average of 3.5 points less pain in the percutaneous group.

Until recently, most of the relevant published studies on MIS-SI joint fusion, though generally positive in efficacy and safety in patients resistant to conservative care, were relatively small, single surgeon series, non-randomized and non-controlled, lacked blind outcomes assessment, and with limited follow-up of 1-2 years (7-18). In a post-market analysis of 5319 patients with a mean follow-up of four months (range 0-30) performed by one of the manufacturers (SI Bone, San Jose, CA, USA), 3.8% reported complications (e.g., pain, nerve impingement, and recurrent SIJ pain), and improper device placement occurred in 1.4%, all presenting in the early post-operative period (19).

However, more sophisticated studies are emerging. Duhon reports early (12 months in 172 patients) positive results of an ongoing multicenter, prospective, single arm trial (Sacroiliac Joint Fusion With iFuse Implant System (SIFI)) of minimally invasive SI joint fusion using iFuse (20). While there were significant reductions in pain and disability from baseline, the study suffers from being non-controlled, and only reporting relatively short-term data. The first multi-center prospective, randomized controlled trial comparing MIS-SI joint fusion (N=102) with specific, targeted non-surgical treatment (N=46) of the SI joint was recently published (21). By 6 months, success as measured by a composite of pain reduction, absence of serious adverse events or neurological worsening, and absence of repeat surgery, was found in 81.4% of operative patients and 24% of non-surgical patients. Clinically important (15 points) Oswestry Disability Index (ODI) improvement at 6 months occurred in 75% and 27.3% of surgical and non-surgical patients, respectively.

In summary, MIS-SI joint fusion studies, while still moderate in terms of data quality and follow-up time, consistently show improved pain scores with fewer complications than open fusion in patients with non-infectious, non-traumatic related SI pain. This along with positive, and society guideline recommendations (NASS, ISASS) leads CGS to cover MIS-SI joint fusion for the following carefully selected patients per recently published NASS guidelines (22).

Indications of Coverage

Minimally-invasive surgical (MIS) fusion of the sacroiliac (SI) joint is considered medically necessary when ALL of the following criteria are met:

• Have moderate to severe pain with functional impairment and pain persists despite a minimum six months of intensive nonoperative treatment that must include medication optimization, activity modification, bracing, and active therapeutic exercise targeted at the lumbar spine, pelvis, SIJ and hip including a home exercise program
  
• Patient’s report of typically unilateral pain that is caudal to the lumbar spine (L5 vertebrae), localized over the posterior SIJ, and consistent with SIJ pain
  
• A thorough physical examination demonstrating localized tenderness with palpation over the sacral sulcus (Fortin’s point, i.e. at the insertion of the long dorsal ligament inferior to the posterior superior iliac spine or PSIS) in the absence of tenderness of similar severity elsewhere (e.g. greater trochanter, lumbar spine, coccyx) and that other obvious sources for their pain do not exist
  
• Positive response to a cluster of 3 provocative tests (e.g. thigh thrust test, compression test, Gaenslen’s test, distraction test, Patrick’s sign, posterior provocation test).
  
• Absence of generalized pain behavior (e.g. somatoform disorder) or generalized pain disorders (e.g. fibromyalgia)
  
• Diagnostic imaging studies that include ALL of the following:
  
  
  • Imaging (plain radiographs and a CT or MRI) of the SI joint that excludes the presence of destructive lesions (e.g. tumor, infection), fracture, traumatic SIJ instability, or inflammatory arthropathy that would not be properly addressed by percutaneous SIJ fusion
    
  • Imaging of the pelvis (AP plain radiograph) to rule out concomitant hip pathology
    
  • Imaging of the lumbar spine (CT or MRI) to rule out neural compression or other degenerative condition that can be causing low back or buttock pain
  
  
• At least 75 percent reduction of pain for the expected duration of two anesthetics (on separate visits each with a different duration of action), and the ability to perform previously painful maneuvers, following an image-guided, contrast-enhanced intra-articular SIJ injection.
  
• A trial of at least one therapeutic intra-articular SIJ injection (i.e. corticosteroid injection)