Rationale
The index 2014 ISASS Policy Statement - Minimally Invasive Sacroiliac Joint Fusion was generated out of necessity to provide an ICD9-based background and emphasize tools to ensure correct diagnosis. A timely ICD10-based 2016 Update provides a granular threshold selection with improved level of evidence and a more robust, relevant database.
Introduction
The sacroiliac joints (SIJ) are diarthrodial articulations of the sacrum and ilium. The SIJ serves as the biomechanical mediator between the spine and pelvis. The subchondral bone, capsule, and surrounding ligaments of the SIJ are innervated by spinal nerves.1
Sacroiliac joint (SIJ) pain is likely responsible for chronic back pain in some patients; furthermore in some studies the prevalence is reported to be 15-30%.2–6 Convergence of the sensory pathway from the hip, the SIJ and the lumbar spine may result in overlap of pain patterns from dysfunction of these structures. As such, proper SIJ pain diagnosis is key to appropriate patient management. Patients with SIJ pain typically report pain in the buttock(s), with possible radiation into the groin or upper legs. Specific physical examination tests that stress the SIJ (e.g., distraction test, compression test, thigh thrust, FABER (Patrick's) test, Gaenslen's maneuver) are typically performed in the physician's office; in combination, these tests are thought to be predictive of SIJ pain.7
The spectrum of pain and disability from SIJ dysfunction is wide. Patients may be affected mildly or may have substantial functional impairment (e.g., cannot sit or stand for more than five minutes, cannot perform normal activities of daily living (ADLs), cannot walk up or down stairs, may require a wheelchair). Patients with chronic SIJ dysfunction seeking surgical treatment have marked impairment of quality of life,8 similar to that observed in other conditions commonly treated surgically.9 Apart from ankylosing spondylitis, in which MRI can show edema consistent with inflammation, imaging of the SIJ typically does not provide valuable diagnostic information. In many cases, imaging can show non-specific findings in the SIJ.10 Rather, imaging is used to ensure that the patient does not have alternative diagnoses that could mimic SIJ pain (e.g., hip osteoarthritis, occasionally L5/S1 spine degeneration) (Table 1).
The diagnosis of SIJ pain is confirmed by performing a fluoroscopy-guided percutaneous SIJ block with local anesthetic (e.g., lidocaine). An acute reduction in typical pain indicates a positive test, suggesting that the injected joint is a pain generator. A study of patients undergoing blinded injection of saline or local anesthetic showed markedly high responses to the latter, validating the test.11 Because other pathologic processes can coexist with SIJ pain, physicians should discuss with patients the degree to which treatment of the SIJ may relieve overall pain and disability without addressing other pain generators.
Occasionally, bilateral SIJ pain can occur. Diagnosis of bilateral SIJ pain should be made on the basis of typical history (bilateral symptoms), physical examination showing positive responses to SIJ-stressing maneuvers bilaterally, and bilateral acute pain relief upon bilateral, fluoroscopy-guided SIJ block.
While a marked response to SIJ block might be predieted to reassure the physician that treatment will produce larger responses to anatomic-based treatment, published data suggest little, if any, relationship. In two large prospective clinical trials of SIJ fusion, patients with suspected SIJ pain were included only if intraarticular SIJ block resulted in a 50% or greater amount of acute pain relief within 60 minutes after the block. The degree of improvement at 6 and 12 months after SIJ fusion was unrelated to the degree of acute pain relief during the block.12 In a retrospective analysis of predictors of outcome success after RF ablation of lateral branches of the sacral nerve roots in patients with SIJ pain, no relationship was observed between response to lateral branch block or SIJ anesthesia and response to RF ablation.13 Randomized trials of RF ablation of lateral branches of the sacral nerve roots excluded patients with <75% pain reduction after lateral branch block (one block in Cohen et al.14 and two blocks in Patel et al.15), leaving open the question of whether the selected threshold was appropriate.
Multiple non-surgical treatments for SIJ pain are available, including pain medications (e.g., non-steroid anti-inflammatory agents), physical therapy, steroid injections into the SIJ, and radiofrequency ablation of the sacral nerves and SIJ fusion. While pain medications may relieve temporarily pain and/or disability, they have not been shown to impact the underlying disease process, and opioid addiction remains an important public health concern. Apart from a single clinical trial in post-partum pelvic pain (probably related to the SIJ),16 the effectiveness of physical therapy for chronic SIJ dysfunction has not been demonstrated. Two randomized trials have shown that RF ablation of lateral branches of sacral nerve roots can temporarily reduce SIJ pain.14, 15 One-year follow-up from one RF ablation randomized trial showed modest pain reduction.17 Responses in the non-surgical arms of two prospective randomized trials showed little, if any, improvement at 6 months.18, 19 Given the absence of published outcomes data supporting long-term pain relief from non-surgical treatment, patients with a diagnosis of SIJ pain who experience pain for a minimum of six months and who do not respond to an adequate course of non-surgical treatment may be considered for SIJ fusion.
Coverage Rationale for Open and Minimally Invasive SIJ Fusion
Open fusion of the SIJ, first reported in the early 1900s,20 can provide pain relief but recovery times are long and complication rates are high,21–25 intraoperative times, bleeding and hospital length of stay are more prominent compared to minimally invasive SIJ fusion,26 and recovery times are long and may require prolonged postoperative rehabilitation. Therefore, open fusion of the SIJ is best performed on patients who are not candidates for minimally invasive SIJ fusion.
Minimally invasive fusion of the SIJ has been performed with several types of implants, including triangular, porous, titanium coated implants,19, 27–33 hollow modular screws,34–36 titanium cages,37, 38 and allograft dowels21 (Table 2). Minimally invasive fusion aims to permanently stabilize the SIJ but avoid the morbidity of the open procedure.
Two surgical approaches are commonly used for minimally invasive SIJ fusion:
A lateral transarticular approach, in which devices are placed across the SI joint from lateral to medial. Multiple devices are FDA cleared for this approach for conditions including sacroiliac joint disruptions and degenerative sacroiliitis. However, the vast majority of the published clinical literature for this approach reports use of triangular titanium implants (iFuse Implant System, SI-BONE, Inc.).
A posterior approach, in which devices are placed into the ligamentous portion of the joint via dissection of the multifidus muscle and removal of ligaments covering the outer posterior surface of the joint. In the posterior approach, a portion of the interosseous SIJ ligament is sometimes removed.
Published Literature
Published outcomes data for minimally invasive SIJ fusion using a posterior approach are scarce. One cohort reported marginal response to use of cages placed into the SIJ through a posterior approach.38 For the lateral approach, 3 retrospective case series (describing two cohorts) using hollow modular anchor (HMA) screws suggest reasonable 2- and 3-year outcomes.35, 36 HMA screws are not FDA-cleared for SIJ fusion.and are not available for use in the U.S. The remaining published literature on SIJ fusion through a lateral approach used triangular titanium implants (iFuse Implant System, SI-BONE, Inc.). This literature includes:
A US multicenter, randomized clinical trial (INSITE, n = 148)19 with an embedded cost-utility analysis39
A European multicenter, randomized clinical trial (iMIA, n = 103, in press18)
A US prospective multicenter single-arm clinical trial (n = 172) with 24-month follow-up31
A multicenter case series32
3 comparative studies comparing open and iFuse-based SI joint fusion26, 45, 46
An analysis of implant survivorship47
A systematic review and meta-analysis48
A systematic review.49 Both systematic reviews focused on laterally-based procedures and products. The majority of cohorts were triangular titanium implants.
Taken together, these studies provide substantial evidence that minimally invasive SIJ fusion with triangular titanium implants improves pain, function and quality of life. In both randomized trials, pain relief, disability reduction and improvement in quality of life were markedly higher in SIJ fusion subjects compared to non-surgically treated subjects. Specifically, in the SIJ fusion group of the US randomized trial,19 mean SIJ pain improved from 82.3 at baseline to 30.4 at the 6-month follow-up (52.0-point improvement, p<.0001) and 28.3 at the 12-month follow-up (54.2-point improvement, p<.0001). Mean changes in the non-surgical group were not clinically significant (mean 12 points). Similarly, in the SIJ fusion group, mean ODI decreased from 57.2 at baseline to 29.9 at month 6 and 28.1 at month 12 (improvements of 27.4 and 29.3 points, respectively). In contrast, mean ODI decreased by only 4.6 points in the non-surgical group. In the European randomized trial,18 Mean pain scores improved in the SIJ fusion group from 77.7 at baseline to 34.4 at 6 months (a 43.3 point improvement p<.0001) vs. 73.0 to 67.8 (an improvement of 5.7 points, p=.1105) in the non-surgical group. ODI improved by 20 points more in the surgical vs. non-surgical groups 9p<.0001). EQ-5D time trade-off index also improved more in the surgical vs. non-surgical group.
In a multicenter retrospective review of 263 patients undergoing either open or minimally invasive SIJ fusion with triangular titanium implants, minimally invasive SIJ fusion was associated with statistically significant and clinically marked decreases in operating room time (mean 163 minutes for open vs. 70 minutes for minimally invasive), decreased blood loss (mean 288 cc vs. 33 cc), and decreased length of stay (5.1 vs. 1.3 days) as well as improved relief of pain at 1 (-2.7 points on 0-10 scale vs. -6.2 points) and 2-year (-2.0 vs. -5.6 points) follow-up (all differences are statistically significant.).26 Finally, two published studies report that favorable outcomes achieved at one year are sustained long term (up to 5 years).30, 33
The complication rate for minimally invasive SIJ fusion with triangular titanium implants is low.50 Revision rates over 4 years (3.5%47) are substantially lower than after lumbar fusion surgery, and revision rates in long-term retrospective30, 33 and prospective studies19, 31 have confirmed this low rate. Revisions can be required in the immediate postoperative period or after many months. Early revisions may include the need to reposition an implant that is impinging on a sacral nerve or removal of an implant due to infection. Revision rates with other products are unknown. Screw-based devices rely upon different fusion strategies (HA coating, fenestrations within the screws, etc.) with different biomechanics (threaded screws vs. triangular implants that are impacted across the SI joint). Regardless of implant, salvage revision remains challenging.
Bilateral Procedures
In cases of bilateral SIJ pain, bilateral SIJ fusion may occasionally be indicated and is usually performed serially to minimize the impact on rehabilitation (i.e., patients who undergo simultaneous bilateral fusion procedures may be wheelchair or bedbound for several weeks, possible slowing overall recovery).
Indications/Limitations of Coverage
Patients who have all of the following criteria may be eligible for minimally invasive SIJ fusion:
Significant SIJ pain that impacts quality of life or significantly limits activities of daily living;
SIJ pain confirmed with at least 3 physical examination maneuvers that stress the SIJ (see list provided above) and reproduce the patient's typical pain.
Confirmation of the SIJ as a pain generator with ≥50% acute decrease in pain upon fluoroscopically guided diagnostic intra-articular SIJ block using local anesthetic. Prospective trials have shown that patients with SIJ pain responses of 50-75% respond to MIS SIJ fusion as well as those with 75-100% acute responses.12
Failure to respond to at least 6 months of non-surgical treatment consisting of non-steroidal anti-inflammatory drugs and physical therapy. Failure to respond means continued pain that interferes with activities of daily living and/or results in functional disability;
Additional or alternative diagnoses that could be responsible for the patient's ongoing pain or disability have been considered. Physicians should take into account that patients can have multiple pain generators and addressing just one pain generator may not adequately relieve disability or all back pain.
Minimally invasive SIJ fusion is NOT indicated for patients with the following:
Less than 6 months of SIJ pain and/or functional impairment
Failure to pursue conservative treatment of the SIJ (unless contra-indicated);
Pain not confirmed with a diagnostic SIJ block;
Presence of other pathology that would substantially prevent the patient from deriving benefit from SIJ fusion
Bilateral SIJ pain is not uncommon. Diagnosis of bilateral SIJ pain must be made on the basis of a history of bilateral pain, bilateral elicitation of pain on physical examination maneuvers that stress each SIJ, and acute bilateral decrease in pain upon fluoroscopically-guided intra-articular SIJ block with local anesthetic. Bilateral SIJ fusion is probably best performed serially as successful treatment of one side may improve pain/disability to a degree acceptable by the patient. SIJ fusion of the contralateral side may be necessary if contralateral SIJ pain continues and disability is significant for the patient. If bilateral fusion is performed at the same operative session, the surgeon must document both medical necessity and why serial fusion is not indicated in the patient.
It is expected that a person would not undergo more than one SIJ fusion per side per lifetime except in the rare case that a revision is needed.
Coding
The American Medical Association recommends minimally invasive SIJ fusion be coded using CPT code 27279. Revision and/or removal of the SIJ implant would typically be coded using 22899 (unlisted procedure, spine) or 27299 (unlisted procedure, pelvis or hip joint) depending on the type of approach and procedure performed, whether within the global period of the fusion, or not.
Documentation Requirements
A complete history and physical documenting the likely existence of SIJ pain;
Performance of a fluoroscopically-guided SIJ block on the affected side (or both sides, see discussion above) which shows at least a 50% acute reduction in pain;
A course of conservative treatment to include use of non-steroidal anti-inflammatory drugs and one of the following: (1) an adequate period of rest, (2) an adequate course of physical therapy wherein the physical therapist specifically documents lack of response to treatment
SIJ pain has continued for a minimum of six months; and
All other diagnoses that could be causing the patient's pain have been considered and the physician believes that SIJ fusion is clinically required.
Surgeon Qualifications
Minimally invasive SIJ fusion is a surgical procedure performed by orthopedic or neurologic surgeons who have successfully completed a residency in that specialty as well as at least one specialized training course in the procedure. Training should include device placement in cadavers under supervision of a surgeon experienced in the procedure.
Surgeons performing minimally invasive SIJ fusion should be specifically credentialed and/or privileged by at least one hospital to perform the procedure.
Coverage/Conclusion
The utilization of minimally invasive surgical approach for SIJ fusion has become a recognized safe, predictable and preferred surgical method for the management of intractable, debilitating primary or secondary SIJ pain disorders.57
The ISASS policy does not endorse any specific MIS SIJ System. There are numerous devices available that have received FDA 510 (k) clearance for use in minimally invasive/percutaneous sacroiliac joint fusion stabilization. The instrumentation utilized in a MIS SIJ procedure is the purview of surgeon preference.58
- Copyright © 2016 ISASS - This manuscript is generously published free of charge by ISASS, the International Society for the Advancement of Spine Surgery