Managing pain with SI joint fusion and nerve ablation

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As an IR at the University of Alabama at Birmingham, my practice focuses on interventional spine and pain intervention. Many of these procedures are done using basic fluoroscopy and US guidance. However, IRs have imaging knowledge and capabilities far exceeding what has traditionally been available to other specialties. Using these skills, we are able to make procedures safer and faster for patients. Extension of our skillset into the musculoskeletal system and pain management is a natural step. There is high demand for these procedures, making this space “blue water,” or a ripe opportunity, for our specialty. Douglas Beall, MD, FSIR, has been at the forefront of expansion in this space and shared insight on how he approaches sacroiliac (SI) joint instability and percutaneous fusion.

Junjian Huang, MD: How did you get started with percutaneous SI joint fusion?

Douglas Beall, MD, FSIR: I began working with percutaneous SI joint fusion by treating sacral traumatic fractures. I would span them with 7.0 mm partially threaded screws, often combined with bone cement depending on the density of the bone. These screws had a tendency to loosen and back out. This caused us to change to fully threaded screws, which held better but still did not predictably stay in place without occasionally backing out. The sacral fractures often involved the SI joint, and fusion of the joint was a routine way of treating patients with pelvic ring injuries.

These strategies had a significant overlap with the treatment of sacral insufficiency fractures that were seen almost exclusively in patients with severe osteoporosis and were treated very effectively with sacroplasty.1 Sacroplasty was used for some sacral fractures and could be combined with screw fixation when the sacral fracture gap was large due to fracture displacement or an oligotrophic nonunion fracture.

SI joint fusion was also used in patients with chronic pelvic instability, which typically affected the SI joints and the pubic symphysis. These joints often had demonstrable instability and were difficult to treat with the smaller 7.0 mm screws even when cement was added. Additionally, the failure rate was unacceptably high. In 2009, SI-BONE launched triangular titanium bars that were designed for SI joint fusion, and by 2015 there was a Category I CPT code for SI joint fusion and a Level I randomized control trial supporting the efficacy of this technique.

The first dorsally placed allograft appeared in 20122 and quickly gained popularity in treating distraction-type arthrodesis due to the ease of the approach and the optimal safety of the procedure. I adopted this technique for certain patients who couldn’t undergo general anesthesia or who had a contraindication to the lateral approach for SI joint arthrodesis. Interventionalists began to adopt this approach for SI fusion and the increased popularity caught the attention of the surgeon community who maintained that this was a different procedure and should have a different CPT code associated with it.

In 2023, dorsal SI joint fusion with an intra-articular allograft was assigned a Category III code, which was converted back to a new Category I code in 2024 based on a new CPT application submitted with supportive data. The new code for the dorsal approach is 27278 as compared to the original lateral or posterolateral approach code of 27279 or the open SI joint fusion code, which is 27280. Despite the slightly more invasive nature of the latter two codes, all of the techniques of SI joint fusion have become far less invasive over the past 2 decades.

JH: Can you walk me through how to evaluate a patient and determine if they are an ideal candidate for this procedure?

DB: Selecting patients for SI joint fusion is very different from selecting patients for lumbar fusion. The SI joint only moves a small amount (1.4–3.1 mm in any direction)3 and degenerative changes are common at an early age even in patients with no SI joint pain.4 Unlike many other joints that may undergo fusion, imaging mainly plays a role in SI joint fusion to detect pathologic entities that are not amenable to fusion, such as inflammatory changes or erosions from spondyloarthropathies, sacral fracture, or a tumor such as a chordoma. No imaging modality has been shown to have good diagnostic value for detecting a painful SI joint. In lieu of that, a combination of physical examination tests for SI joint pain and the patient response to an SI joint injection test is used to determine the optimal candidates for SI joint fusion.

Even before these tests are used to select the patients, the clinical history is very important for determining the patients with SI joint pain as opposed to those with lower lumbar and hip pain—both of which can present with similar signs and symptoms. Patients who have prior trauma or a previous long- or short-segment fusion that traverses L5-S1 are typical for those who develop SI joint pain. So are women with long-standing, postpartum pelvic instability.

Once at-risk patients are identified, SI joint injections may be performed. We look for an injection test result of 75% or more pain relief, which indicates a positive test and an appropriate candidate for SI joint fixation. The physical examination tests for SI joint pain, which are critical for evaluating for SI joint pain, include:

  • Pelvic compression test
  • Pelvic distraction test
  • Sacral thrust test
  • Gaenslen’s (pelvic torsion) test
  • Faber’s test
  • Thigh thrust test

SI joint dysfunction is diagnosed when three of six physical examination tests are positive. When three out of five physical examination tests are positive there is an 85% pretest probability that an SI joint injection will be successful,5 and there is a 91% sensitivity and 78% specificity for SI joint–related pain.6

JH: How has this been received by competing specialties in your area?

DB: The introduction of less invasive techniques for SI joint fusion has not only resulted in shorter surgery times, less blood loss and fewer days in the hospital, but it also results in better clinical outcomes versus open SI joint fusion.7,8 The minimally invasive technique has also attracted more interventional pain management and interventional radiology physicians who now routinely perform SI joint fusions. In fact, data from the Center for Medicare and Medicaid Services have shown that the majority of minimally invasive SI joint fusions are performed by individuals in the “nonsurgical specialties.”9 There has also been rapid growth in the minimally invasive procedures that are offered in ambulatory surgical and outpatient centers.9

Although there has been some controversy in who should be performing SI joint fusions, the overall sentiment is that the minimally invasive procedure has been very beneficial in regard to patient safety and efficacy across the different specialties that perform these techniques.

JH: How do you go about obtaining training/credentialing to perform percutaneous SI joint fusion?

DB: In addition to formal programs such as residencies or fellowships that focus on interventional musculoskeletal procedures, training may also be obtained in industry-, society- and foundation-sponsored courses. Credentialing to be able to perform these procedures can sometimes be difficult to obtain given the wide variety of specialties performing these procedures along with the heterogeneity of the education, training and experience of physicians performing SI joint fusions. The challenge, of course, is to determine the physician’s competency on a relatively new procedure often without much experience using the predicate device.

Additionally, a credentialing committee can be fraught with turf war controversies that may complicate an otherwise straightforward credentialing process. Credentialing support letters may be helpful. These letters can include a procedure technique document, a sample operative note, the appropriate CPT codes, results of a pertinent clinical trial and a training certificate. In addition to credentialing, each practitioner should determine whether their malpractice coverage is sufficient to cover an SI fusion procedure. If not, an insurance rider (insurance endorsement) may possibly be obtained to add the procedure to the list of covered items.

JH: What can SIR and its membership do to help promote percutaneous SI joint fusion as a procedure in IR? 

DB: SIR has effectively advocated for minimally invasive surgical and procedural techniques for many years. However, as a relatively new procedure that is in the musculoskeletal intervention category, minimally invasive SI joint fusion is somewhat outside the boundary of procedures typically thought of as performed by interventional radiology.

The first step to assist the IRs performing SI joint fusion is to recognize that our colleagues are routinely performing this procedure, with some practitioners performing it quite often. The Society has already demonstrated support for the procedure and has instituted training courses and lecture topics at the annual meeting reflecting this interest in managing patients with SI joint dysfunction.

The primary role of SIR at this point is to continue to support its members as they expand their minimally invasive repertoire for treating SI joint dysfunction and other musculoskeletal issues. The initial improvements in this treatment and others have been profoundly positive and this trajectory should be aspired to in the future. ­

References

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  2. Endres S, Ludwig E. Outcome of distraction interference arthrodesis of the sacroiliac joint for sacroiliac arthritis. Indian J Orthop. 2013 Sept–Oct;47­(5):437–42.
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  6. Laslett M, Young SB, Aprill CN, McDonald B. Diagnosing painful sacroiliac joints: A validity study of a McKenzie evaluation and sacroiliac provocation tests. Aust J Physiother. 2003;49(2):89–97. doi: 10.1016/s0004-9514(14)60125-2.
  7. Smith AG, Capobianco R, Cher D, Rudolf L, Sachs D, Gundanna M, Kleiner J, Mody MG, Shamie AN. Open versus minimally invasive sacroiliac joint fusion: a multi-center comparison of perioperative measures and clinical outcomes. Ann Surg Innov Res. 2013 Oct 30;7(1):14. doi: 10.1186/1750-1164-7-14. PMID: 24172188. PMCID: PMC3817574.
  8. Ledonio CG, Polly DW Jr, Swiontkowski MF. Minimally invasive versus open sacroiliac joint fusion: Are they similarly safe and effective? Clin Orthop Relat Res. 2014 Jun;472(6):1831–8. doi: 10.1007/s11999-014-3499-8. PMID: 24519569. PMCID: PMC4016421.
  9. Hersh AM, Jimenez AE, Pellot KI, Gong JH, Jiang K, Khalifeh JM, Ahmed AK, Raad M, Veeravagu A, Ratliff JK, Jain A, Lubelski D, Bydon A, Witham TF, Theodore N, Azad TD. Contemporary trends in minimally invasive sacroiliac joint fusion utilization in the Medicare population by specialty. Neurosurgery. Epub 2023 Dec 1;93(6):1244–50. doi: 10.1227/neu.0000000000002564. PMID: 37306413.