The Rise of Sacroiliac Joint Fusions

With more than $85 billion in annual expenditures, low back pain remains the fifth most common reason for a medical visit.[1] Significant efforts have been made toward better understanding the various etiologies of low back pain.

The sacroiliac (SI) joint has been cited as a source of pain in up to 15% of patients seen by physicians for low back pain, but it is often misdiagnosed as lumbar pathology.[2] Therefore, it is no surprise that healthcare expenditure has steadily increased in both diagnosing and treating SI dysfunction.

The SI joint connects the spine to the pelvis, transferring loads between the lower extremities and the spine. However, the SI joint functions poorly in resisting shear loads, predisposing patients to increased rates of degeneration.[3] Increased rates of degeneration exist in cases of repetitive stress, pregnancy, seronegative spondyloarthropathies, obesity, trauma, and degeneration, leading to asymmetric pain that can mimic disc degeneration and radiculopathy. A diagnosis of SI joint dysfunction has demonstrated a moderate to high sensitivity and specificity in patients who demonstrate a positive response to at least three provocative examination maneuvers.[4]

Fluoroscopic- and ultrasound-guided SI joint injections offer both diagnostic and therapeutic utility. Patients who report a significant improvement in pain after an injection may be further diagnosed as having SI joint dysfunction.

Why the Increase in Utilization?

Similar to the attention paid to improving our understanding of the SI joint and low back pain, there has been an increase in the utilization of SI joint fusion procedures. Since its inception in 2015, the minimally invasive surgery (MIS) SI joint fusion Current Procedural Terminology (CPT) code, 27279, has seen increased volume and reimbursement rates.[5] Furthermore, both open and MIS SI joint fusions have seen an increase in procedure volume of 2,351% in the decade spanning from 2010 to 2020, though MIS SI joint fusions have rapidly outgrown their open counterparts. Whether this relates to an increase in diagnosis or increase in reimbursement is up for debate.

Additionally, open SI joint fusions are becoming more commonplace in long-construct deformity procedures. The current literature has suggested widely varying rates of pseudarthrosis from the single digits to as high as 70%.[6] In addition to alternative techniques such as multiple rod constructs, surgeons addressing spinal deformities have incorporated S2-alar-iliac (S2AI) screws instead of iliac screws to fur- ther minimize the risks of pseudarthrosis and reoperation.[7,8] However, literature is lacking as to whether these patients have been evaluated for dysfunction prior to undergoing fusion of the SI joint. The longer-term effects of fusing a previously asymptomatic SI joint has yet to be clearly demonstrated.

Various medical technology companies have offered more advanced procedural solutions to addressing SI joint dysfunction, instilling confidence in surgeons hoping to successfully treat SI joint pain. Training laboratories, demonstrations, and surgeon support teams have attempted to unify our understanding of how to successfully perform an SI joint fusion. Industry-led growth has been well demonstrated in the pharmaceutical arena and is becoming more apparent in spine surgery. This often leads surgeons toward trialing new techniques and implants with the hopes of improving outcomes. Together, this has led to a rapid growth in SI joint fusions.

Is the Increase in Utilization Warranted?

Early outcome studies following MIS SI joint fusions demonstrated excellent medium- and long-term outcomes. However, these studies were inherently biased.[9] A systematic review of 16 articles suggested excellent outcomes ranging from 18% to 100%.[10] Much of the meaningful literature with long-term follow-up, however, involved authors with significant conflicts of interest. In patients correctly diagnosed as having SI joint dysfunction, outcome studies continue to demonstrate good results at 24 and 60 months.[9,11] Currently, there is a double-blinded multicenter randomized controlled trial with ongoing enrollment comparing MIS SI joint fusion with a sham operation, but the results have yet to be published.[12]

Furthermore, no argument can be made for the utility of an MIS technique for SI fusion. Transiliac and MIS dorsal approaches minimize the dissection and tissue disruption required to perform a successful arthrodesis, and techniques have been described using both fluoroscopy and navigation with excellent results.[13] As robotics and navigation increase its reach beyond pedicle screws, placement of SI screws from various approaches may even allow for improved biomechanics. “Crossed” techniques of placing implants from a lateral, posterolateral, or even posterior approach allow for improved biomechanical stability across the SI joint and may become more reproducible with the use of robotics and navigation.

Final Thoughts

The SI joint is prone to biomechanical loads that can increase degeneration and is a site of wear in various medical conditions. Together, the SI joint plays a role in low back pain and can mimic lumbar pathology, often going underappreciated as a diagnosis and thus delaying appropriate medical care. Recent advancements in diagnosis include correlating physical examination findings with injections and have allowed surgeons to better appreciate the SI joint as a pain generator, though confirming that the SI joint is indeed the primary cause of low back pain has remained a challenge. While no surgery is perfect, MIS techniques can mitigate many of the potential complications and improve outcomes. Patients who are successfully diagnosed as having SI joint dysfunction may benefit from an MIS SI joint fusion across a minimally mobile joint that is often a significant source of pain.

References

1. Martin BI, Deyo RA, Mirza SK, et al. Expenditures and health status among adults with back and neck problems. JAMA. 2008;299(6):656-664.

2. Dreyfuss P, Dreyer SJ, Cole A, Mayo K. Sacroiliac joint pain. J Am Acad Orthop Surg. 2004;12(4):255-265.

3. Kiapour A, Joukar A, Elgafy H, Erbulut DU, Agarwal AK, Goel VK. Biomechanics of the sacroiliac joint: anatomy, function, biomechanics, sexual dimorphism, and causes of pain. Int J Spine Surg. 2020;14(Suppl 1):3-13.

4. Falowski S, Sayed D, Pope J, et al. A review and algorithm in the diagnosis and treatment of sacroiliac joint pain. J Pain Res. 2020;13:3337-3348.

5. Federico VP, Zavras AG, Butler A, Nolte MT, Munim MA, Lopez GD, et al. Medicare reimbursement rates and utilization trends in sacroiliac joint fusion [published online ahead of print May 16, 2023]. J Am Acad Orthop Surg. doi:10.5435/JAAOS-D-22-00800

6. Kim YJ, Bridwell KH, Lenke LG, Rhim S, Cheh G. Pseudarthrosis in long adult spinal deformity instrumentation and fusion to the sacrum: prevalence and risk factor analysis of 144 cases. Spine. 2006;31(20):2329-2336.

7. Elder BD, Ishida W, Lo SFL, et al. Use of S2-Alar-iliac screws associated with less complications than iliac screws in adult lumbosacropelvic fixation. Spine. 2017;42(3):E142-E149.

8. Ishida W, Elder BD, Holmes C, et al. Comparison between S2-alar-iliac screw fixation and iliac screw fixation in adult deformity surgery: reoperation rates and spinopelvic parameters. Global Spine J. 2017;7(7):672-680.

9. Rudolf L, Capobianco R. Five-year clinical and radiographic outcomes after minimally invasive sacroiliac joint fusion using triangular implants. Open Orthop J. 2014;8:375-383.

10. Zaidi HA, Montoure AJ, Dickman CA. Surgical and clinical efficacy of sacroiliac joint fusion: a systematic review of the literature. J Neurosurg Spine. 2015;23(1):59-66.

11. Duhon BS, Bitan F, Lockstadt H, et al. Triangular titanium implants for minimally invasive sacroiliac joint fusion: 2-year follow-up from a prospective multicenter trial. Int J Spine Surg. 2016;10:13.

12. Randers EM, Gerdhem P, Dahl J, Stuge B, Kibsgård TJ. The effect of minimally invasive sacroiliac joint fusion compared with sham operation: study protocol of a prospective double-blinded multicenter randomized controlled trial. Acta Orthop. 2022;93:75-81.

13. Polly DW Jr, Holton KJ. Minimally invasive sacroiliac joint fusion: a lateral approach using triangular titanium implants and navigation. JBJS Essent Surg Tech. 2020;10(4):e19.00067.

AUTHOR

Arash J. Sayari, MD

From Rush University Medical Center in Chicago, Illinois.