| Coverage Policy Manual | |
| Policy #: | 2006032 |
| Category: | Surgery |
| Initiated: | October 2006 |
| Last Review: | May 2024 |
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| Interspinous and Interlaminar Stabilization/Distraction Devices (Spacers) | |
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| Description: |
Interspinous spacers are small devices implanted between the vertebral spinous processes. After implantation, the device is opened or expanded to distract the neural foramina and decompress the nerves. One type of interspinous implant is inserted between the spinous processes through a small (4-8 cm) incision and acts as a spacer between the spinous processes, maintaining flexion of that spinal interspace. The supraspinous ligament is maintained and assists in holding the implant in place. The surgery does not include any laminotomy, laminectomy, or foraminotomy at the time of insertion, thus reducing the risk of epidural scarring and cerebrospinal fluid leakage. Other interspinous spacers require removal of the interspinous ligament and are secured around the upper and lower spinous processes.
Interlaminar spacers are implanted midline between the adjacent lamina and spinous processes to provide dynamic stabilization either following decompression surgery or as an alternative to decompression surgery. Interlaminar spacers have 2 sets of wings placed around the inferior and superior spinous processes. They may also be referred to as interspinous U. These implants aim to restrict painful motion while enabling normal motion. The devices (spacers) distract the laminar space and/or spinous processes and restrict extension. This procedure theoretically enlarges the neural foramen and decompresses the cauda equina in patients with spinal stenosis and neurogenic claudication.
Regulatory Status
Three interspinous and interlaminar stabilization and distraction devices have been approved by the U.S. Food Drug Administration (FDA) through the premarket approval (FDA product code: NQO):
The Superion® Indirect Decompression System (formerly Interspinous Spacer) is indicated to treat skeletally mature patients suffering from pain, numbness, and/or cramping in the legs secondary to a diagnosis of moderate degenerative lumbar spinal stenosis, with or without Grade 1 spondylolisthesis, confirmed by Xray, MRI and/or CT evidence of thickened ligamentum flavum, narrowed lateral recess, and/or central canal or foraminal narrowing. It is intended for patients with impaired physical function who experience relief in flexion from symptoms of leg/buttock/groin pain, numbness, and/or cramping, with or without back pain, and who have undergone at least 6 months of non-operative treatment.
FDA lists the following contraindications to use of the Superion® Indirect Decompression System:
The coflex® Interlaminar Technology implant (Paradigm Spine) is a single-piece U-shaped titanium alloy dynamic stabilization device with pairs of wings that surround the superior and inferior spinous processes. This device was previously called the Interspinous U. The coflex® is indicated for use in 1- or 2-level lumbar stenosis from L1-L5 in skeletally mature patients with at least moderate impairment in function, who experience relief in flexion from their symptoms of leg/buttocks/groin pain, with or without back pain, and who have undergone at least 6 months of nonoperative treatment. The coflex® is intended to be implanted midline between adjacent lamina of 1 or 2 contiguous lumbar motion segments. Interlaminar stabilization is performed after decompression of stenosis at the affected level(s).
FDA lists the following contraindications to use of the coflex®:
The FDA labeling also contains multiple precautions and the following warning: "Data has demonstrated that spinous process fractures can occur with coflex® implantation."
At the time of approval, the FDA requested additional postmarketing studies to provide longer-term device performance and device performance under general conditions of use. The first was the 5-year follow-up of the pivotal investigational device exemption trial. The second was a multicenter trial with 230 patients in Germany who were followed for 5 years, comparing decompression alone with decompression plus coflex®. The third, a multicenter trial with 345 patients in the U.S. who were followed for 5 years, compared decompression alone with decompression plus Coflex (FDA, 2012). FDA product code: NQO.
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Policy/ Coverage: |
Effective July 2018
Does Not Meet Primary Coverage Criteria Or Is Investigational For Contracts Without Primary Coverage Criteria
Interspinous or interlaminar distraction devices as a stand-alone procedure for treatment of pain secondary to spinal stenosis does not meet member benefit certificate primary coverage criteria that there be scientific evidence of effectiveness. The X-STOP® device, although FDA approved, is still currently being studied in an FDA regulated condition of approval study to evaluate long-term safety and efficacy.
For contracts without primary coverage criteria, interspinous or interlaminar distraction devices as a stand-alone procedure for treatment of pain secondary to spinal stenosis is considered investigational and is not covered. Investigational services are exclusions in the member benefit contract.
The use of an interlaminar stabilization device following decompression surgery does not meet member benefit certificate primary coverage criteria that there be scientific evidence of effectiveness in improving health outcomes.
For members with contracts without primary coverage criteria, the use of an interlaminar stabilization device following decompressive surgery is considered investigational. Investigational services are specific contract exclusions in most member benefit certificates of coverage.
Interspinous distraction devices as a treatment of neurogenic intermittent claudication do not meet member benefit certificate primary coverage criteria that there be scientific evidence of effectiveness in improving health outcomes.
For members with contracts without primary coverage criteria, interspinous distraction devices as a treatment of neurogenic intermittent claudication are considered investigational. Investigational services are specific contract exclusions in most member benefit certificates of coverage.
Effective Prior to July 2018
Interspinous distraction devices
The implantation of an interspinous distraction device for treatment of leg and/or back pain secondary to spinal stenosis does not meet member benefit certificate primary coverage criteria that there be scientific evidence of effectiveness. The X-STOP® device, although FDA approved, is still currently being studied in an FDA regulated condition of approval study to evaluate long-term safety and efficacy.
For contracts without primary coverage criteria, the implantation of an interspinous distraction device for treatment of pain secondary to spinal stenosis is considered investigational and is not covered. Investigational services are exclusions in the member benefit contract.
Interspinous distraction devices as a treatment of neurogenic intermittent claudication do not meet member benefit certificate primary coverage criteria that there be scientific evidence of effectiveness in improving health outcomes.
For members with contracts without primary coverage criteria, interspinous distraction devices as a treatment of neurogenic intermittent claudication are considered investigational. Investigational services are specific contract exclusions in most member benefit certificates of coverage.
Interlaminar stabilization device
The use of an interlaminar stabilization device following decompressive surgery does not meet member benefit certificate primary coverage criteria that there be scientific evidence of effectiveness in improving health outcomes.
For members with contracts without primary coverage criteria, the use of an interlaminar stabilization device following decompressive surgery is considered investigational. Investigational services are specific contract exclusions in most member benefit certificates of coverage.
Effective prior to May 2013
The implantation of an interspinous distraction device for treatment of leg and/or back pain secondary to spinal stenosis does not meet member benefit certificate primary coverage criteria that there be scientific evidence of effectiveness. The X-STOP® device, although FDA approved, is still currently being studied in an FDA regulated condition of approval study to evaluate long-term safety and efficacy.
For contracts without primary coverage criteria, the implantation of an interspinous distraction device for treatment of pain secondary to spinal stenosis is considered investigational and is not covered. Investigational services are exclusions in the member benefit contract.
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| Rationale: |
This policy was developed as a result of the FDA approval of the X-STOP® Interspinous Process Decompression System.
One prospective randomized trial with follow-up of both groups to two years has been reported for this device. The control group was medical (non-operative) therapy including epidural injection. Using the entire study population, the Zuckerman paper noted an improvement of 45% over the mean baseline Symptom Severity Score in the treated patients at two years compared with 7% improvement in the control group. Anderson and colleagues reported a success rate of 63% in treated patients compared with 13% of controls; their study reported on a subset of 75 randomized patients who had spondylolisthesis (out of the total group of 191 patients with one or two level lumbar spinal stenosis.) Four year follow up has been reported for 18 of the treated patients in the study.
While these results are promising, some questions still remain. One question is about the durability of the device. Another concern about the study is the lack of blinding and related bias. There also are concerns about more patients with incomplete follow up in the control (medical) treatment group. At one year, there was complete data on 68/91 control patients compared to 88/100 in the experimental group. Additional studies to better control for potential biases and methodological issues need to be completed.
The manufacturer is required to conduct post marketing studies to determine the safety and effectiveness of the device.
2009 Update
A search of the MEDLINE database was conducted through September 2009 did not identify any evidence that would alter the conclusions reached above. Quality of life data (SF-36) were reported from the Zucherman trial (Zucherman, 2005). The patients, who had to meet a number of inclusion/exclusion criteria, were assessed at baseline and at 6 weeks, 6 months, 1 year, and 2 years following the initial treatment. The X-STOP group showed improvements (by single-factor ANOVA or t-test) in both physical and mental component scores compared to both baseline and control subjects. As indicated, there was a large loss to follow-up (42%) in the medical-treatment group; 6% of the experimental and 26% of the control subjects underwent laminectomy. Another industry-sponsored trial examined the neural foramina and spinal canal area in 26 patients with spinal stenosis and neurogenic intermittent claudication who had not responded to nonoperative treatment (Siddiqui, 2006). Positional MRI showed a 21% increase in spinal canal area when patients were in seated-neutral and a 23% increase when erect. The neural foramen was significantly increased on the left side only with extension (20%) and flexion (19%). Additional measured areas were found to increase with double-level surgeries.
The addition of a DIAM implant to simple lumbar surgery (laminectomy and/or microdiscectomy) was examined in a case-control study of 62 patients (Kim, 2007). Radiographic imaging, pain scores, and clinical assessments at a mean of 12 months’ follow-up showed no differences in the patients who had received both surgery and the implant in comparison with patients who had undergone laminectomy/microdiscectomy alone.
Verhoof et al reported that, in a cohort of 12 consecutive patients with symptomatic lumbar spinal stenosis caused by degenerative spondylolisthesis who were treated with X-STOP and followed up for a mean of 30.3 months, 8 patients had complete relief of symptoms postoperatively while 4 had no relief (Verhoof, 2008). Recurrence of pain, neurogenic claudication, and worsening of neurological symptoms were observed in 3 patients within 24 months. Postoperative radiographs and magnetic resonance imaging (MRI) did not show changes in percentage of slip or spinal dimensions. Seven patients had posterior fusion within 24 months. The authors did not recommend the device for treatment of spinal stenosis complicating degenerative spondylolisthesis. Siddiqui and colleagues conducted a prospective observational study of 40 consecutive patients implanted with the X-STOP device (Siddiqui, 2007). Patients were evaluated at 3, 6, and 12 months using the Zurich Claudication Questionnaire, Oswestry Disability Index, and SF-36. Only 24 patients (60%) completed all questionnaires and were analyzed. By 12 months, clinically significant improvement in symptoms and physical function was noted by 54% and 33% of the 24 patients, respectively. Postoperatively, 29% of patients required caudal epidural after 12 months for recurrence of symptoms of neurogenic claudication. The authors concluded that while the device offers significant short-term improvement over a 1-year period, results are less favorable than those reported in a multicenter randomized trial. Brussee et al reviewed pre- and postoperative Zurich and SF-36 questionnaires completed by 65 patients who received the X-STOP device between 2003 and 2006 (Brusee, 2008). A good outcome was achieved by 31% of patients. Good outcome was not related to BMI (body-mass index) or number of implanted devices, but was related to the absence of orthopedic co-morbidity or male gender. The authors concluded that X-STOP does improve the clinical situation; however a good outcome is achieved less often than previously reported. These recent publications did not lead to a change in the current policy statement. Data from rigorous randomized controlled trials are needed to adequately evaluate this device.
No interspinous distraction devices other than the X-STOP have received FDA Premarket Approval. Results of case series of the Wallis, Diam and CoFlex devices have been reported. Floman and colleagues report that implantation of the Wallis interspinous implant failed to reduce the incidence of recurrent disc herniations (Floman, 2007). In their series of 37 consecutive patients, 5 were diagnosed with recurrent herniation between 1 and 9 months after surgery; 2 of them underwent additional discectomy and fusion.
Chou and colleagues presented a review of evidence related to surgical treatments for low back pain (Chou, 2009). They concluded on the basis of the randomized trial data noted above, that the evidence was fair quality and that an interspinous spacer device is superior to nonsurgical therapy for 1- or 2-level spinal stenosis with symptoms relieved with forward flexion, but that insufficient evidence exists to judge long-term benefits or harms. The guidelines developed from the evidence review indicated that interspinous spacer devices, based on fair evidence, have a B recommendation (panel recommends that clinicians consider offering the intervention.
The North American Spine Society guidelines on the diagnosis and treatment of degenerative lumbar spinal stenosis conclude that with a single Level 1 study on the X-STOP, “there remains insufficient evidence to make a recommendation.”
The X-Stop is currently being studied in an FDA regulated study to evaluate the long-term safety and effectiveness of the device. At this time, there is insufficient evidence of long-term safety and effectiveness of interspinous distraction devices in improving health outcomes and the policy remains unchanged.
2010 Update
A PubMed search through October, 2010, did not identify reports of results of randomized controlled trials of X-Stop. There continue to be a number of ongoing trials including the Condition of Approval Study, NCT00517751, required by the FDA. X-Stop is an active comparator in several trials of yet to be FDA approved devices that include the In-Space (Synthes Spine), the VertiFlex® Superion™, and the FLEXUS™.
Kuchta et al. (2009) reported two-year results of X-Stop implantation in a single center, one or two levels, in 175 patients with neurologic intermittent claudication. The mean VAS (leg pain) score, 61.2% preoperatively, was reduced to 39% at 6 weeks and 39% 24 months postoperatively. The Oswestry disability index was 32.6% preoperatively and 22.7% at 6 weeks, 20.3% at 24 months postoperatively on average.
Burnett et al. (2010) reported the cost-effectiveness of some treatment strategies for lumbar stenosis,. comparing conservative treatment, decompressive laminectomy and X-Stop. They concluded that lumbar laminectomy appears to be the most cost-effective treatment strategy for patients with symptomatic lumbar stenosis.
In a 2010 review article, Yi and McPherson focused on neurogenic intermittent claudication and lumbar spinal stenosis with a literature review of X-Stop. Despite improvement in lumbar spinal and neural foraminal dimensions after X-Stop implantation, in cadaveric specimens and in vivo, and reported overall safety and efficacy of the device, they recommend caution. “Large, randomized, and truly long-term studies with consistent outcome measures and follow up are currently lacking. As a result, the definitive efficacy and safety of this implant remains debatable.”
No medical literature has been indentified that would support a revision of the coverage statement.
2011 Update
A search of the MEDLINE database was conducted through February, 2011. A series of 175 patients were treated at a German center between February 2003 and June 2007 (Kuchta, 2009). Mean VAS score was reduced from 61.2 to 39 on a 100 point scale at 6 weeks postoperatively and maintained to the 2 year evaluation. Mean Oswestry Disability Index (ODI) scores were 32.6 (range 8-80, SD: 16.0) preoperatively, 22.7 (range 0-85, SD:15.6) at 6 weeks postoperatively, and 20.3 (range 0-42, SD:17.5) at 2 years. No complications were associated with use of the device. Eight patients required removal of the device and microsurgical decompression because of unsatisfactory outcome.
In a 2010 paper, Rolfe and colleagues evaluated outcomes of a series of 179 patients with and without scoliosis in order to test a contraindication which limits X-STOP use to patients with a maximum scoliosis of 25 degrees (Rolfe, 2010). Patients, who received the device between January 2006 and May 2007, were divided into 3 groups: Group 1 (controls, n=116) without scoliosis, Group 2 patients with low scoliosis (11-25 degrees, n=41), and group 3 (high scoliosis, n=22). At one year, 56% of Group 1 and Group 2 patients, but only 18% of Group 3 patients, achieved improvement of 15 or more points on Oswestry Disability Index (ODI). Satisfaction rates were 76% for Group 1, 78% for Group 2, and 59% for Group 3. On average, all 3 groups improved for each outcome: Group 1 (ODI 17.3, VAS 2.0, standing time 39 minutes, and walking time 43 minutes), Group 2 (ODI 20.0, VAS 1.9, standing time 65 minutes, and walking time 64 minutes), Group 3 (ODI 7.2, VAS 0.9, standing time 18 minutes, and walking time 16 minutes). The authors conclude that surgeons and patients must be aware that overall lumbar scoliosis more than 25 degrees may portend less favorable outcomes.
Two papers focus on complications. Barbagallo analyzed complications in a series of 69 patients and proposed an anatomic scoring system for patient selection (Barbagallo, 2009). At a mean follow-up of 23 months, 8 complications were recorded: 4 device dislocations and 4 spinous process fractures. Bowers et al. reviewed records of 13 patients implanted with the X-STOP device at one US center. (13) Nine patients had severe and 4 had moderate stenosis. Average follow-up was 42.9 months (range, 3-48 months). Initially, pain improved an average of 72%, however preoperative pain returned in 77% of the patients. The overall complication rate was 38%, including 3 spinous process fractures and 2 instances of new onset radiculopathy. Eleven of the 13 patients required additional spinal surgery.
The MEDLINE search found the literature dominated by reports from non-US centers of devices that have not received FDA approval though a number of them are in trials at US centers. Kabir et al., in a 2010 systematic review, observed that apart from the 2 randomized controlled trials, other studies with X-STOP were not of high methodological quality (Kabir, 2010). The authors observe that results at 2 years were analyzed using only the Zurich Claudication Questionnaire (ZCQ) while analysis of one-year results also included the SF-36. They also note concerns about the trial raised by the FDA: First, the block randomization employed could potentially be used to select patients more likely to respond to the intervention. Second, outcomes in both groups were worse than expected suggesting that power calculations were invalid. Third, results from one center were clearly superior to those of other centers. Four-year follow-up included only 18 of the original 100 patients, and ODI scores were reported instead of ZCQ scores. Studies of the other devices (DIAM, Coflex, Wallis, DIAM) included in the review show satisfactory outcomes to varying degrees however “due to small numbers and poor design of studies, it is difficult to clearly define indications for their use in lumbar degenerative disease”. The authors conclude that X-STOP may improve outcome compared to nonoperative treatment in a select group of patients 50 or more years of age with radiologically confirmed lumbar canal stenosis and neurogenic claudication who have improvement of symptoms on flexion, however they suggest that further good quality trials are required to clearly identify indications for the use of the devices. As of January 2011, only the X-STOP device has FDA approval for use in the US and this policy does not address other devices.
Technology Assessments, Guidelines and Position Statements
The National Institute for Health and Clinical Excellence (NICE) published guidance in November 2010 stating that “Current evidence on interspinous distraction procedures for lumbar spinal stenosis causing neurogenic claudication shows that these procedures are efficacious for carefully selected patients in the short and medium term, although failure may occur and further surgery may be needed. The evidence reviewed consisted mainly of reports on X-STOP.
In 2007, the North American Spine Society published new guidelines on the diagnosis and treatment of degenerative lumbar spinal stenosis. They concluded that with a single Level 1 study on the X-STOP, “there remains insufficient evidence to make a recommendation.” These guidelines remain current in January 2011.
2012 Update
A search of the PubMed database was conducted through September 2012. A 2011 study assessed implant survival in a retrospective analysis of 46 consecutive patients (61 devices) with a minimum follow-up of 24 months (Tuschel). Inclusion criteria were the same as in the pivotal randomized trial by Zucherman et al. (2005). At a mean follow-up of 34 months (range, 24-70 months), 14 patients (30.4%) had undergone revision surgery to remove the implant. Most revisions occurred within the first 12 months. Revisions were due to lack of improvement (n=6), worsening of low back pain (n=1), recurrence of symptoms after initial good outcome (n=4), implant dislocation (n=2), and fracture of a spinous process (n=1). Two additional patients were lost to follow-up, and one patient was unhappy with the result and did not complete the questionnaires. Kaplan-Meier analysis predicted an implant survival of 34% at 53 months. The mean time until implant removal was 15.4 months. In the remaining 29 patients who did not undergo revision surgery, clinical outcomes improved significantly. VAS for lumbar pain decreased from 4.8 to 3.2 and VAS for leg pain decreased from 5.4 to 2.0. The ODI improved from 39.9 to 24.7 and the SF-36 physical component score improved from 30.2 to 38.4. The overall clinical success rate was 36%, defined as an improvement of the ODI by at least 15 points or a patient’s satisfaction rating of “very satisfied”. The authors concluded that clinical outcomes after X-STOP implantation might be considerably less favorable than what has been previously published and that further research is needed to improve patient selection.
In 2012 Patil, et al. reported on a retrospective analysis conducted of a consecutive series of 31 patients who received the X-STOP interspinous process distraction device as treatment for neurogenic intermittent claudication. Outcome was assessed at an average of 2 years after surgery by use of the Zurich Claudication Questionnaire (ZCQ), which used the definition of clinical success used in the IDE study. On the basis of the ZCQ, clinically significant improvement occurred in 38% of the evaluable patients (21 patients), compared with 48.4% in the IDE study; at the sites other than those of the device's inventors, the improvement level was 37%. Four patients needed additional surgery, which was a rate comparable with that reported in the IDE study. The success level in the controlled IDE study that established the safety and efficacy of the X-STOP device was achieved in a representative patient cohort that did not necessarily meet all the strict requirements of the IDE plan. Nevertheless, the overall results were not good, suggesting that the ZCQ definition of success might not have captured the true outcome of surgical treatment with the X-STOP device.
Summary
While results of the studies of the X-STOP device are promising, some questions remain. One major issue relates to durability and the need for long-term (more than 2 years) outcome data. There are also questions about patient section criteria, for instance, should patients with any degree of spondylolisthesis be excluded from this treatment? Overall, high-quality comparative data are quite limited. Additional randomized studies with longer (more than 2 years) follow-up that better control for potential biases and avoid other methodological issues, including follow-up of patients in the control group and consistent use of outcome measurements, need to be completed.
The following clinical trials are on-going:
No medical literature was indentified that would support a revision of the coverage statement.
2014 Update
A literature search conducted through April 2014 did not reveal any new information that would prompt a change in the coverage statement. The key identified literature is summarized below.
A randomized non-inferiority trial of the X-STOP compared to decompressive surgery was published by Bjorn et al. in 2013 (Bjorn, 2013). One hundred patients with symptomatic one- or two-level lumbar spinal stenosis and neurogenic claudication relieved on flexion were included in the study. Blinding of patients and evaluators was not described. There was a decrease in surgical time (62 vs. 98 minutes) and blood loss (54 vs. 262) with insertion of the X-STOP, although statistical analysis was not reported. Both intention-to-treat analysis and as-treated analysis at 6, 12, and 24 months found no significant differences between the groups on the patient-reported ZCQ, visual analog score (VAS) for leg and back pain, or Short Form (SF)-36. Thirteen patients (26%) in the X-STOP group had additional surgery (typically decompression) compared to 3 patients (6%) in the decompression group, and there was 1 spinous process fracture. The X-STOP patients who later underwent decompression were not considered to be treatment failures.
In 2010, Richter et al. reported a prospective case control study of the Coflex® device in 60 patients who underwent decompressive surgery (Richter, 2010). Two-year follow-up from this study was published in 2012/2013 (Richter, 2012). Decompression involved a partial laminotomy, removal of ligamentum flavum, and undercutting facetectomy. The surgeon determined whether the midline structures were preserved or resected and whether the Coflex® device was implanted (1 or 2 levels). The indications for the two groups were identical, and use of the device was considered incidental to the surgery. No significant differences were observed between the groups on the Oswestry disability index (ODI), the Roland-Morris disability questionnaire (RMS), VAS for pain, and pain-free walking distance. At 2-year follow-up, there were no significant differences between the 2 groups for any of the outcome measures in this non-randomized controlled cohort study, suggesting that additional placement of the Coflex® device does not improve the clinical outcome of decompressive surgery. Randomized controlled trials are needed to determine the efficacy of the Coflex® interlaminar implant with greater certainty.
2015 Update
A literature search conducted through June 2015 did not reveal any new information that would prompt a change in the coverage statement. The key identified literature is summarized below.
Systematic Reviews
Two recent systematic reviews compared use of interspinous distraction devices versus traditional decompressive surgery for lumbar spinal stenosis (LSS). In 2014, Wu and colleagues conducted a meta-analysis of 2 randomized controlled trials (RCTs) and 3 non-randomized prospective comparative studies (Wu, 2014). There were 204 patients in the interspinous spacer group and 217 patients in the decompressive surgery group. The interspinous spacers that were studied were the X-STOP, Aperius, Coflex, DIAM, and distraXion. Pooled analysis showed no significant difference between the spacer and decompression groups for low back pain, leg pain, Oswestry Disability Index (ODI), Roland Disability Questionnaire (RDQ) or complications. However, the traditional decompressive surgery group had a significantly lower incidence of reoperation, with 11 of 160 cases requiring reoperation compared to 31 of 161 cases in the interspinous spacer group (relative risk [RR] 3.34; 95% CI: 1.77, 6.31).
A 2015 meta-analysis by Hong and colleagues included 20 studies with 3,155 patients in the interspinous spacers group and 50,983 patients treated with open decompression (Hong, 2015). Devices studied were the X-STOP, DiAM, Aperius, Coflex, Wallis, and SPIRE. Results of this meta-analysis were similar to those obtained in the more selective analysis by Wu. There was no significant difference between the 2 types of procedures for improvement rate, ODI, or visual analog scale (VAS) for back or leg pain. Although postoperative complication rate, perioperative blood loss, hospitalization time, and operation time were lower/shorter in the interspinous spacer group, the reoperation rate was higher (16.5% vs 8.7%).
Puzzilli and colleagues reported a multicenter controlled trial of X-STOP versus non-surgical management in 2014 (Puzzilli, 2014). A total of 542 patients with lumbar spinal stenosis (LSS) and intermittent claudication relieved on flexion were enrolled. All patients had failed a 6-month trial of conservative therapy (medical and/or physical). Initially patients were randomized, but randomization to conservative management was terminated after the first 120 patients due to poor outcomes. These patients were followed for a minimum of 3 years. By 3 years, the overall failure rate was 12.3% of X-STOP patients compared to 50% of patients with continued non-surgical management.
X-STOP versus Decompression
Two randomized trials have compared implantation with X-STOP versus decompression.
In 2015, Lonne and colleagues reported a trial of X-STOP versus minimally invasive decompression in 96 patients with symptoms of neurogenic intermittent claudication relieved on flexion (NCT00546949) (Lonne, 2015a). Intention-to-treat analysis showed no significant differences between the groups in primary and secondary outcome measures at up to 2-year follow-up. However, the number of patients having secondary surgery due to persistent or recurrent symptoms was significantly higher in the X-STOP group (25% vs 5%, odds ratio = 6.5). In addition, 2 patients had fracture of the spinous process and 1 had dislocation of the implant (Lonne, 2015b). Three patients in the decompression group had secondary surgery during the first hospital stay due to hematoma. Mean days of rehabilitation were 66 for X-STOP and 48 for surgical decompression. The study was terminated after planned mid-term analysis due to the higher reoperation rate with X-STOP.
Superion versus X-STOP
In 2015, results were published from an FDA-regulated, multicenter randomized, investigational device exemption (IDE), non-inferiority trial comparing the Superion interspinous spacer with the X-STOP (Patel, 2015). A total of 391patients with intermittent neurogenic claudication despite 6 months of nonsurgical management were enrolled, randomized and implanted with either Superion or X-STOP spacers, and followed for 2 years. The primary endpoint was a composite of clinically significant improvement in at least 2 of 3 ZCQ domain scores compared with baseline, freedom from reoperation, revision, removal, or supplemental fixation at the index level, freedom from epidural steroid injection or nerve block within 12 weeks of the 2-year visit, freedom from rhizotomy or spinal cord stimulator at any level, and freedom from major implant or procedure-related complications. The primary non-inferiority endpoint was met, with a Bayesian posterior probability of 0.993. However, 111 patients (28%, 54 Superion and 57 XSTOP) were withdrawn from the study during follow-up due to a protocol-defined secondary intervention. Modified intent-to-treat analysis showed clinical success (improvement ≥20 mm/100 for leg pain in 76% to 77% of patients and for back pain in 67% to 68% of patients, with no significant differences between groups. At 2-years, ODI success was achieved in 63% of Superion patients and 67% of XSTOP patients (p=0.061).
Rates of complications and reoperations (44 [23.2%] Superion and 38 [18.9%] XSTOP) were similar between groups. Spinous process fractures, reportedly asymptomatic, occurred in 16.4% of Superion patients and 8.5% of XSTOP patients. Interpretation of this study is limited by the lack of a control group treated by surgical decompression.
Wallis versus Decompression
In 2014, Marsh and colleagues reported a randomized controlled trial that compared decompression alone (n=30) versus decompression with a Wallis implant (n=30 (Marsh, 2014). Follow-up at an average of 40 months showed no significant differences between the groups in VAS for back or leg pain or in the ODI. Improvement in back pain was 3.5 out of 10 with the Wallis implant compared with 2.7 without (p=0.1926). Improvement in ODI was 19.3 with the Wallis implant compared with 10.6 without (p=0.0787). Additional study in a larger population is needed.
A European multicenter, randomized, double-blind trial (FELIX) compared implantation of coflex® (without bony decompression) versus bony decompression in 159 patients with intermittent neurogenic claudication due to lumbar spinal stenosis. Functional outcomes measured by the ZCQ and Modified Roland-Morris Disability Questionnaire (RMDS), and pain measured with VAS and the McGill Pain Questionnaire, were similar in the 2 groups at 1-year follow-up. Surgery time was shorter, but reoperation rates due to absence of recovery were higher in the coflex® group compared with the bony decompression group (29% vs 8%, p<0.001). For patients with 2-level surgery, the reoperation rate was 38% for coflex® versus 6% for bony decompression (p<0.05). At 2 years, reoperations due to absence of recovery had been performed in 33% of the coflex® group compared with 8% of the bony decompression group (Moojen, 2015). VAS back pain at final follow-up was also higher in the coflex® group (36 mm vs 28 mm/100).
Ongoing and Unpublished Clinical Trials
Ongoing
NCT0534235 Industry sponsored or cosponsored; Post-Approval Clinical Study Comparing the Long Term Safety and Effectiveness of Coflex vs. Fusion to Treat Lumbar Spinal Stenosis; planned enrollment of 396; projected completion date October 2015.
NTC01316211 Industry sponsored or cosponsored; A 5 year comparative evaluation of clinical outcome in the treatment of degenerative spinal stenosis with concomitant low back pain by decompression with and without additional stabilization using the coflex® Interlaminar Technology; planned enrollment of 245; projected completion date March 2016.
NCT00517751 Industry sponsored or cosponsored; Treatment of Lumbar Spinal Stenosis with X-STOP® PEEK Spacer in Moderately Symptomatic Patients – Condition of Approval Study (COAST); planned enrollment of 240; projected completion date July 2022.
Interspinous and interlaminar implants (spacers) stabilize or distract the adjacent lamina and/or spinous processes and restrict extension to reduce pain in patients with lumbar spinal stenosis and neurogenic claudication. The randomized trials that compare the devices to nonoperative therapy report greater short-term improvements in symptoms and functional status for the device groups. While this establishes that the use of interspinous spacers can lead to better short-term symptom relief than continued conservative therapy, there is a need for longer term (>2 years) outcome data on the durability of symptom relief, the need for repeat procedures, and implant survival. Trials comparing these devices to standard decompressive surgery report that symptomatic outcomes are similar, but there is a higher reoperation rate for the devices compared with standard decompressive surgery. Longer-term studies are in progress as part of the post-approval requirements of the FDA.
2016 Update
A literature search conducted through April 2016 did not reveal any new information that would prompt a change in the coverage statement. The key identified literature is summarized below.
Superion Versus X-STOP
In 2015, 2- and 3-year results were published from an FDA-regulated, industry sponsored, multicenter randomized, investigational device exemption (IDE), non-inferiority trial comparing the Superion ISS with the X-STOP (Patel, 2015). A total of 391patients with intermittent neurogenic claudication despite 6 months of nonsurgical management were enrolled, randomized, and implanted with either Superion or X-STOP spacers, and followed for 2 years. The primary end point was a composite of clinically significant improvement in at least 2 of 3 ZCQ domain scores compared with baseline, freedom from reoperation, revision, removal, or supplemental fixation at the index level, freedom from epidural steroid injection or nerve block within 12 weeks of the 2-year visit, freedom from rhizotomy or spinal cord stimulator at any level, and freedom from major implant or procedure-related complications. The primary noninferiority end point was met, with a Bayesian posterior probability of 0.993. However, 111 patients (28%; 54 Superion, 57 XSTOP) were withdrawn from the study during follow-up due to a protocol-defined secondary intervention. Modified intention-to-treat analysis showed clinical success (improvement, ≥20 mm/100) for leg pain in 76% to 77% of patients and for back pain in 67% to 68% of patients, with no significant differences between groups. At 2 years, ODI success was achieved in 63% of Superion patients and 67% of XSTOP patients (p=0.061). Rates of complications and reoperations (44 [23.2%] Superion, 38 [18.9%]
At 3-year follow-up, there were 120 patients in the Superion ISS group and 129 in the X-STOP group remaining (64% of 391). Of these, composite clinical success was obtained in 52.5% of patients in the Superion ISS group and 38.0% of the X-STOP group (p=0.023). The 36-month clinical outcomes were reported for 82 patients in the Superior ISS group and 76 patients in the X-STOP group (40% of 391). It is not clear from the report whether the remaining patients were lost to follow-up or were considered treatment failures and censured from the results. In addition, interpretation of this study is limited by questions about the efficacy of the comparator and lack of a control group treated by surgical decompression.
Section Summary: Interspinous or Interlaminar Distraction as Stand-Alone Treatment for lumbar spinal stenosis
Overall, use of interspinous or interlaminar distraction devices (spacers) used as a stand-alone treatment for lumber spinal stenosis show high failure and complication rates.
Coflex
The pivotal IDE trial for coflex Interlaminar Technology was a nonblinded randomized multicenter trial of decompression plus coflex compared with decompression plus posterolateral fusion and pedicle screw fixation in patients with low-grade spondylolisthesis. Four year follow-up was reported in 2015 and 5 year follow-up was reported in 2016 (Bae, 2015; Musachio, 2016). A total of 344 patients were randomized in a 2:1 ratio (215 coflex, 107 fusion controls, with 22 protocol violators). This study was conducted in a restricted population with numerous exclusion criteria. Compared with fusion, implantation of the coflex device required less operative time (98.0 minutes vs 153.2 minutes) and resulted in less blood loss (109.7 mL vs 348.6 mL) and a shorter hospital stay (1.9 days vs 3.2 days).
Composite clinical success (a combination of a minimum 15-point improvement in ODI, no reoperations, no device-related complications, and no epidural steroid injections in the lumbar spine) at 24 months achieved non-inferiority compared with posterolateral fusion (66.2% coflex, 57.7% fusion). Secondary effectiveness criteria, which included the ZCQ, VAS for leg and back pain, SF-12, time to recovery, patient satisfaction, and several radiographic end points, tended to favor the coflex group by Bayesian analysis. (In this analysis, non-overlapping confidence intervals imply statistically reliable group differences.) For example, ZCQ composite success was achieved in 78.3% of coflex patients (95% confidence interval [CI], 71.9% to 84.7%) compared with 67.4% of controls (95% CI, 57.5% to 77.3%). The percentage of device-related adverse events was the same for the 2 groups (5.6% coflex, 5.6% control), and a similar percentage of asymptomatic spinous process fractures were observed. In the subset of patients with grade I spondylolisthesis, the coflex ® and fusion groups had similar outcomes in ODI, VAS, and ZCQ, but the reoperation rate trended higher in the coflex® cohort (14.1% vs 5.9%, p=0.18). FDA considered the data in this non-blinded study to support reasonable assurance of safety and effectiveness for device approval, but approval is conditional on 2 additional studies that will provide longer term follow-up (in the IDE cohort) and evaluate device performance under actual conditions of use (decompression alone vs decompression with coflex).
The reported rate of follow-up at 5 years ranged from 40% to 100%, depending on the outcome measured (Musacchio, 2016). For example, the ODI at 6 months was reported for 56% of patients, while major device-related complications and composite clinical success were reported for 100% of patients. Interpretation of the 5-year results is limited by the variable loss to follow-up in outcomes.
In 2015, Roder and colleagues reported a cross registry study that compared lumbar- decompression plus Coflex (SWISSspine registry) to lumbar decompression alone (Spine Tango registry) in 50 pairs matched by a multifactorial propensity score (Roder, 2015). SWISSspine is a governmentally mandated registry from Switzerland for coverage with evidence development. Spine Tango is a voluntary registry from the Spine Society of Europe. Both registries use the numeric rating scale (NRS) for back and leg pain and the Core Outcome Measures Index (COMI) as the patient-based outcome instrument. The COMI consists of 7 questions to evaluate pain, function, wellbeing, quality of life, and disability. At 7 to 9 months follow-up, the Coflex group had greater reduction in NRS back pain (3.8 vs 2.5, p=0.014), NRS leg pain (4.3 vs 2.5, p<0.001), NRS maximum pain (4.1 vs 2.3, p=0.002) and greater improvement in the COMI score (3.7 vs 2.5, p =0.029).
Section Summary: Interlaminar Stabilization Devices Used in Addition to Spinal Decompression Surgery
Use of the Coflex interlaminar implant as a stabilizer after surgical decompression has been studied in 2 different situations, as an alternative to spinal fusion after decompression or as an adjunct to decompression compared to decompression alone. The pivotal RCT, which was conducted in a very selective patient population, showed that stabilization of a decompression with the coflex implant was non-inferior to decompression with spinal fusion. However, 2 non-randomized controlled trials have mixed results on whether use of the implant in combination with decompression improves outcomes compared with decompression alone. The different comparators used in these trials and the very selective patient population in the pivotal trial limits conclusions about the generalizability of these results. Greater certainty about the net health benefit of this device may be obtained when a recently completed and moderately sized RCT on decompression with and without the coflex implant is published.
Summary of Evidence
The evidence for interspinous or interlaminar spacers as a stand-alone treatment in individuals who have spinal stenosis includes several randomized controlled trials (RCTs). Relevant outcomes are symptoms, functional outcomes, quality of life, and treatment-related morbidity. Overall, use of interspinous or interlaminar distraction devices (spacers) used as an alternative to spinal decompression show a high failure and complication rates.
The evidence for interlaminar spacers in individuals who are undergoing surgical decompression for spinal stenosis includes RCTs and non-randomized comparative studies. Relevant outcomes are symptoms, functional outcomes, quality of life, and treatment-related morbidity.
Use of the Coflex interlaminar implant as a stabilizer after surgical decompression has been studied in 2 different situations, as an alternative to spinal fusion after decompression or as an adjunct to decompression compared to decompression alone. The pivotal RCT, which was conducted in a very selective patient population, showed that outcomes following stabilization of a decompression with the coflex implant were not different than decompression with spinal fusion. This study was unblended and had a high rate of missing data for the patient reported measures. There are also 2 non-randomized controlled trials, and these have mixed results on whether use of the implant in combination with decompression improves outcomes compared with decompression alone. The different comparators used in these trials and the very selective patient population in the pivotal trial limits conclusions about the generalizability of these results. Greater certainty about the net health benefit of this device may be obtained when a recently completed and moderately sized RCT on decompression with and without the coflex implant is published. The evidence is insufficient to determine the effects of the technology on health outcomes.
2018 Update
Annual policy review completed with a literature search using the MEDLINE database through June 2018. The key literature is summarized below.
INTERLAMINAR STABILIZATION DEVICES USED WITH SPINAL DECOMPRESSION SURGERY
coflex Device
The pivotal IDE trial for coflex Interlaminar Technology was a nonblinded, randomized, multicenter, noninferiority trial (-10% noninferiority margin) of decompression plus coflex compared to decompression plus posterolateral fusion and pedicle screw fixation in patients with stenosis and up to grade I spondylolisthesis (FDA, 2012; Davis, 2013). Davis et al described detailed inclusion and exclusion criteria (Davis, 2013). Four year follow-up was reported in 2015 and 3- and 5-year follow-ups in 2016.9-11 A total of 344 patients were randomized in a 2:1 ratio (230 coflex, 114 fusion controls). Twenty two patients were not included in the per protocol analysis due to protocol violations, resulting in 215 patients in the coflex group and 107 fusion controls. Compared with fusion, implantation of the coflex device required less operative time (98.0 minutes vs 153.2 minutes), resulted in less blood loss (109.7 mL vs 348.6 mL), and required a shorter hospital length of stay (1.9 days vs 3.2 days).
Composite clinical success at 24 months showed that coflex was noninferior to posterolateral fusion (-10% noninferiority margin). Secondary effectiveness criteria, which included ZCQ score, VAS scores for leg and back pain, 12-Item Short-Form Health Survey] scores, time to recovery, patient satisfaction, and several radiographic end points, tended to favor the coflex group using Bayesian analysis. The percentages of device-related adverse events were similar for the 2 groups. In the subset of patients with grade I spondylolisthesis, the coflex and fusion groups had similar outcomes in ODI, VAS, and ZCQ scores (Davis, 2013). There was a 14.1% incidence of spinous process fractures, which were reported to be mostly asymptomatic. The FDA considered the data in this nonblinded trial to be sufficient to support reasonable assurance of safety and effectiveness for device approval, but approval was conditioned on 2 additional studies to provide longer term follow-up and evaluate device performance under actual conditions of use.
In 2010, Richter et al reported on a prospective case-control study of the coflex device in 60 patients who underwent decompression surgery (Richter, 2010). Two-year follow-up was published in 2014 (Richter, 2014). The surgeon determined whether the midline structures were preserved or resected and whether the coflex device was implanted (1 or 2 levels). The indications for the 2 groups were identical, and use of the device was considered incidental to the surgery. At 1- and 2-year follow-ups, placement of a coflex device did not significantly improve the clinical outcome compared to decompression surgery alone. Some radiologic findings with the coflex device require additional study to determine their clinical significance. In 2013, Tian reported a high rate (81.2%) of heterotopic ossification (HO) at follow-up
(range, 24-57 months) in patients who had received a coflex device (Tian, 2013). In 16 (50%) of 32 patients, HO was detected in the interspinous space but had not bridged the space, while in 2 (6.3%) patients there was interspinous fusion. In the 9 patients followed for more than 3 years, class II (interspinous space but not bridging) and class III (bridging) HO were detected in all 9. In 2016, Lee et al reported erosion around the spinous process and reductions in disc height and range of motion in patients treated with a coflex device and spinal decompression and were at least 24 months of follow-up (Lee, 2016). Erosion around the coflex device, which was observed in 47% of patients, has the potential to result in spinous process fracture or device malposition. Continued follow-up is needed.
2019 Update
A literature search was conducted through June 2019. There was no new information identified that would prompt a change in the coverage statement.
2020 Update
A literature search was conducted through June 2020. There was no new information identified that would prompt a change in the coverage statement.
2021 Update
Annual policy review completed with a literature search using the MEDLINE database through June 2021. No new literature was identified that would prompt a change in the coverage statement. The key identified literature is summarized below.
Another post-hoc analysis of the pivotal RCT evaluated the use of Coflex in patients 65 years or older (Grinberg, 2020). Clinical outcomes (eg, Oswestry Disability Index, visual analog score, Zurich Claudication Questionnaire, epidural injections) were measured out to 60 months. Patients age 65 years or older who received the interlaminar implant with decompression (n=84) had clinical outcomes that were not significantly different to patients 65 years or older who received decompression and fusion (n=57), and to patients younger than 65 who received the interlaminar implant with decompression (n=131). In contrast, perioperative outcomes such as operative time (100 vs 153 min, p<.001), blood loss (106 vs 358 cc, p<.001), and hospital stay (2.1 vs 3.3 days, p<.001) were improved with the interlaminar implant compared to posterolateral fusion.
Zhong et al evaluated perioperative outcomes in a comparative study of 83 patients (Zhong, 2020). Patients who had the coflex interlaminar implant in combination with laminectomy (n=46) had higher estimated blood loss (97.50 ± 77.76 vs 52.84 ± 50.63 mL, p = 0.004), longer operative time (141.91 ± 47.88 vs 106.81 ± 41.30 min, p = 0.001), and longer length of stay (2.0 ± 1.5 vs 1.1 ± 1.0 days, p = 0.001) compared to laminectomy alone (n=37). Total perioperative complications (21.7% vs 5.4%, p = 0.035) and instrumentation related complications (10.9% vs 0% p = 0.039) were also higher in the interlaminar implant cohort.
2022 Update
Annual policy review completed with a literature search using the MEDLINE database through June 2022. No new literature was identified that would prompt a change in the coverage statement. The key identified literature is summarized below.
Zheng et al retrospectively compared the long-term outcomes of coflex plus decompression to decompression plus fusion for lumbar degenerative disease (Zheng, 2021). The coflex group was comprised of 39 patients and the decompression plus posterior lumbar interbody fusion group (PLIF) was comprised of 43 patients. Both groups had a mean follow-up period of 104 months (about 8.7 years). Both the Oswestry disability index and visual analog scale leg and back pain scores of both groups significantly improved compared to the baseline (p<.05 for all), with no difference detected between groups. Compared to the PLIF group, the coflex group displayed preserved mobility (p<.001), shorter duration of surgery (p=.001), decreased amount of blood loss (p<.001), and shorter hospital stay (p=.040).
2023 Update
Annual policy review completed with a literature search using the MEDLINE database through June 2023. No new literature was identified that would prompt a change in the coverage statement. The key identified literature is summarized below.
Hagedorn et al conducted a retrospective study to determine the incidence of lumbar decompression surgery following minimally invasive lumbar decompression or treatment with the Superion interspinous spacer (Hagedorn, 2022). Of the 199 patients included in the final analysis, 57 patients underwent minimally invasive lumbar decompression only, 124 patients underwent treatment with the Superion interspinous spacer only, and 18 patients underwent minimally invasive lumbar decompression followed by treatment with the Superion interspinous spacer. After 2 years of follow-up, subsequent spine surgery was received by 3 patients who initially underwent minimally invasive lumbar decompression and 1 patient who initially underwent treatment with the Superion interspinous spacer. All patients who underwent subsequent surgery were noted to have severe lumbar spine stenosis.
Gilbert et al retrospectively evaluated interlaminar stabilization with coflex following decompressive laminectomy in 20 patients with lumbar stenosis without instability or spondylolisthesis (Gilbert, 2022). The average visual analog scale score for low back pain preoperatively was 8.8, which improved postoperatively to 4.0, 3.7, and 3.9 at 2 months, 6 months, and 1 year, respectively (p<.001). The average visual analog scale score for lower extremity pain preoperatively was 9.0, which improved postoperatively to 2.7, 2.5, and 2.5 at 2 months, 6 months, and 1 year, respectively (p<.001). Furthermore, the average Oswestry Disability Index scores significantly improved from 66.6 preoperatively to 23.8, 23.3, and 24.5 at 2 months, 6 months, and 1 year postoperatively, respectively (p<.001). The difference in visual analog scale or Oswestry Disability Index scores between 2 months, 6 months, and 1 year did not reach statistical significance. The retrospective nature of the study and short follow-up period after surgery limit conclusions on the role of coflex interlaminar stabilization.
In 2022, the American Society of Pain and Neuroscience published a consensus guideline outlining best practices for minimally invasive lumbar spinal stenosis treatment (Deer, 2022). The following recommendation was provided with regard to the use of interspinous spacers:
2024 Update
Annual policy review completed with a literature search using the MEDLINE database through April 2024. No new literature was identified that would prompt a change in the coverage statement. The key identified literature is summarized below.
A systematic review and meta-analysis of RCTs comparing interspinous spacer devices (ISDs) to decompressive surgery for patients with lumbar spinal stenosis was conducted by Xin et al (Xin, 2023). Eight RCTs including patients (N=852) with lumbar spinal stenosis who received either ISD or decompressive surgery were included. Follow-up duration of trials ranged from 6 to 40 months. The pooled data indicated that patients in the ISD group experienced shorter operation time (p=.003) and otherwise similar hospital stay time and dural violation compared to decompressive surgery. After initial ISD or decompressive surgery, there was a significantly higher rate or reoperation after ISD compared to decompression (odds ratio [OR], 3.21; 95% confidence interval [CI], 1.91 tp 5.40; p<.0001). Additionally, in terms of clinical efficacy endpoints, there was no significant difference in mean visual analog scale leg and back pain scores, Oswestry Disability Index scores, or Zurich Claudication Questionnaire symptom severity subscores between groups who received ISD or decompression. There was a significantly lower Zurich Claudication Questionnaire physical function subscore with ISD compared to decompression (mean difference, -0.27; 95% CI, -0.53 to -0.02; p=.03), but the clinical significance is unknown. The studies included X-STOP ISD devices or other, non-FDA approved ISD devices, which contributed to heterogeneity. Additionally, there was no discussion or stratification of patients based on severity of lumbar spinal stenosis.
Whang et al conducted a retrospective, comparative claims analysis using Medicare claims data to compare rates of subsequent interventions between patients with lumbar spinal stenosis treated initially with ISD and open surgery (such as decompression or fusion) (Whang, 2023). Patients were included in the analysis if they were at least 50 years of age with lumbar spinal stenosis and a qualifying procedure during 2017 to 2021 in the Medicare database. Once identified, patients were reviewed from the qualifying procedure until the end of data availability, up to a 3-year follow-up period. Claims data reflected inpatient hospital, outpatient hospital, skilled nursing facility, or home health encounters for Medicare beneficiaries, but not medication coverage. A total of 400,685 patients (mean age, 71.5 years; 50.7% male) received a qualifying procedure (4183 [10%] treated with ISD; 211,014 [52.7%] with decompression alone; 76,935 [19.2%] with decompression + fusion; and 108,553 [27.1%] with fusion alone) and were included in the analysis. Patients who received ISD were older at baseline compared to open surgery groups (p<.0001 vs all 3 surgery groups) and had increased prevalence of comorbidities, including hypertension, osteoarthritis, diabetes, obesity, chronic obstructive pulmonary disease, atrial fibrillation, osteoporosis, and congestive heart failure.
Investigators found that individuals with initial ISD treatment were significantly less likely to receive surgical interventions than comparators in the 3-year follow-up period. Patients receiving open surgery initially were 1.5 to 2.5 times more likely to have subsequent fusion (ISD vs decompression alone: hazard ratio [HR], 1.49; 95% CI, 1.17 to 1.89; p=.001; ISD vs decompression + fusion: HR, 1.78; 95% CI, 1.40 to 2.27; p<.0001; ISD vs fusion alone: HR, 2.54; 95% CI, 2 to 3.23; p<.0001). Patients in the surgery cohorts were also more likely to have other lumbar spine surgeries (all comparisons p<.001), but less likely to have a drug delivery implant (all comparisons p<.001). In patients with at least 3 months of follow-up, the re-operation rates at 3 months were 1.7%, 1.6%, and 2.5% for the decompression, decompression + fusion, and fusion cohorts, respectively, compared to 0.6% re-operation rate for the ISD cohort (all p<.001). Adjusted logistic regression demonstrated that patients receiving decompression initially (with or without fusion) were 2.6 to 2.8 times more likely to have a re-operation at 3 months compared to ISD patients, and patients receiving initial fusion were 3.9 times more likely to receive re-operation compared to ISD. Short-term life-threatening events within 30 days were 2.4 to 6.4 times more likely to occur in the open surgery cohorts compared to ISD, driven primarily by blood loss associated with fusion procedures and re-admission (all p<.001). Additionally, patients in the open surgery cohorts were 1.3 to 2.4 times more likely to have a long-term complication (all p<.001) and 1.6 to 3 times more likely to have sustained a spinous process fracture compared to ISD (all p<.001). This study has many limitations. Firstly, there are many limitations inherent to claims analyses, including the possibility of coding or data entry errors and the omission of clinical details not needed to justify payment. For example, diagnosis codes identified in claims data lack clinical context, such as the severity of lumbar spinal stenosis or postoperative complications, as well as other prior therapies. Claims data also does not capture patient-reported outcomes, such as visual analog scale scores or Zurich Claudication Questionnaire scores, limiting the ability to determine true efficacy. It is unknown if authors were able to see when a patient was lost to follow-up due to death or end of Medicare coverage, as these rates were not reported. Additionally, since the baseline characteristics of patients receiving ISD indicated that these patients may be inherently sicker than those receiving open surgery, we need clinical context to infer if the reason they did not receive additional surgical procedures post initial ISD placement is because they truly didn't require intervention or they were too sick to tolerate the procedure.
Rosner et al also conducted a retrospective Medicare claims analysis to determine rates of subsequent spinal procedures between individuals receiving ISD alone versus minimally invasive lumbar decompression (MILD) during 2017 to 2021 (Rosner, 2024). Patients receiving ISD and MILD were matched 1:1 using propensity score matching based on demographics and clinical characteristics. A total of 3614 patients from each group were included after matching (mean age, 74 years; mean follow-up, 20 months). At 20 months of follow-up, the ISD cohort showed lower rates of any subsequent surgical intervention (13.9% vs 17.2%; p<.001) and lumbar spinal stenosis surgical intervention (11% vs 14.8%; p<.001) compared to the MILD cohort. There were no significant differences in safety endpoints between the cohorts, including postoperative complications or life-threatening complications. Authors concluded that the safety was comparable between procedures, with a lower re-operation rate at 20 months after ISD compared to MILD. Limitations are similar to the other claims analysis, since the study did not examine changes in symptoms, functionality, or pain. Because the enrollment criteria was the same as that in Whang et al, there may have been patients included in both analyses. Patients were also not randomized to treatment groups and MILD and ISD do not always have identical clinical indications, which could increase the risk of implicit bias in patient selection.
In 2022, ASPN also published evidence-based clinical guidelines informed by a systematic review of randomized controlled trials on interventional treatments for low back pain (Sayed, 2022). The following recommendation was provided with regard to the use of interspinous spacers:
In 2019, a Department of Health & Human Services inter-agency task force released a report on pain management best practices (HHS, 2019). The report provides best practices for development of effective pain management plans using a patient-centered approach in the diagnosis and treatment of acute and chronic pain. All of their statements are on generalized pain and their recommendations relate to gaps in comprehensive pain plan development. In their report, regarding interspinous process spacer devices, they state: "research has shown that interspinous process spacer devices can provide relief for patients with lumbar spinal stenosis with neuroclaudication." The guidelines do not compare therapies to each other and is not informed by a systematic review, it only offers various options to consider when building a pain management plan for a patient.
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