Medical Policy

This document addresses four (4) different types of devices used during or instead of some spinal surgery procedures. These devices can be divided into two categories: motion preserving stabilization systems and rigid stabilization systems.

Motion Preserving Stabilization Systems include the following types of devices:

1. Dynamic pedicle screw-associated stabilization devices are used with spinal fixation to help hold spinal segments in place while still allowing some movement after surgery.
2. Dynamic interspinous process spacer devices and interlaminar spacer devices are designed for the treatment of spinal stenosis in the lumbar spine. Spinal stenosis is a narrowing of one or more of the spaces within the spine, which can compress the spinal cord and/or spinal nerve roots which can result in compression of the neural elements. These devices are intended to indirectly decompress the spinal canal or foramina while preserving some motion.
3. Functional facet replacement devices have been proposed as an alternative to spinal fusion for some individuals undergoing decompression surgery as a treatment for spinal stenosis. These devices aim to stabilize the spine while preserving some motion.

Rigid Stabilization Systems include the following types of devices:

1. Interspinous and interlaminar non-pedicle fixation devices are designed to achieve rigid spinal fixation for spinal fusion. These fixation devices are different from motion-preserving interspinous and interlaminar spacers and other motion-preserving stabilization systems.

Note: For a high-level overview of this document, please see “Summary for Members and Families” below.

Investigational and Not Medically Necessary:

The following types of spinal surgery devices are considered investigational and not medically necessary for all indications:

1. Dynamic pedicle screw-associated stabilization devices; and
2. Dynamic interspinous process spacer devices and interlaminar spacer devices; and
3. Functional facet replacement devices; and
4. Rigid interspinous and interlaminar non-pedicle fixation devices.

This document describes clinical studies and expert recommendations, and explains why certain devices used during spinal surgical procedures are not appropriate. The following summary does not replace the medical necessity criteria or other information in this document. The summary may not contain all of the relevant criteria or information. This summary is not medical advice. Please check with your healthcare provider for any advice about your health.

Degenerative Spine Disease and Some Options for Treatment

Spine disease can cause many health-related problems, including pain, numbness, weakness, bladder and other organ dysfunction, or trouble walking. Several implanted devices have been proposed to treat spine problems, including flexible stabilization devices, interspinous spacers, facet replacement devices, and interspinous process fixation devices. Some are designed to hold the spine in place while allowing some movement. Others are designed to open spaces where nerves pass through or help support spinal fusion. These devices may have possible benefits, such as shorter surgery time, less blood loss, or fewer repeat surgeries in some studies. However, they also have risks, such as infection, problems with loosening or moving screws, device movement, bone fracture, repeat surgery, or continued pain.

What the Studies Show

Studies of flexible stabilization devices, such as the Isobar™ Spinal System, Dynesys^® Spinal System, and Dynamic Soft Stabilization (DSS™), show mixed results. Some studies found less pain or fewer repeat surgeries, but others did not show better pain or function compared with standard spinal fusion. Many studies were small, did not follow people long enough to show long-term impact, or did not include strong comparison groups. Better studies are needed to know if these devices improve long-term health.

Studies of interspinous spacer devices for spinal stenosis also show mixed results. Some people had short-term improvement, but these devices did not work better than standard decompression surgery for pain, function, or disability. Several studies found higher repeat surgery rates with interspinous spacers. Facet replacement devices, such as the Total Posterior Spine System, showed promising short-term results in one study, but longer follow-up is needed to show if the results last over time. To date, the available studies of interspinous process fixation devices are limited, and some reports found serious issues such as spine fractures or other complications. More research is needed to compare these devices with standard spinal fixation.

Is this clinically appropriate?

These implanted spine devices are not clinically appropriate because they have not been proven to improve health better than standard treatments. This includes flexible intervertebral stabilization devices, implanted devices for spinal stenosis, and interspinous process fixation devices. Studies have not shown clear long-term benefits, and some devices may increase the chance of repeat surgery or device-related problems. Better studies are needed to know if these devices improve pain, function, safety, and long-term health.

(Return to Description/Scope)

Summary

Dynamic Pedicle Screw-Associated Stabilization Devices

Studies on dynamic pedicle screw-associated stabilization devices like Isobar, Dynesys Spinal System, and Dynamic Soft Stabilization (DSS) System (Paradigm Spine, LLC, New York, NY) suggest these devices may offer some benefits over traditional spinal fusion for degenerative lumbar spine conditions, such as preserving motion and reducing adjacent segment disease (ASD). For example, the Isobar system showed improved pain and function over 24 months and was associated with shorter surgery times and less blood loss in a meta-analysis. However, long-term evidence remains limited. Similarly, the Dynesys system was linked to lower revision rates and less adjacent segment degeneration in some studies, but overall, it did not lead to significantly better pain or function compared to fusion. A separate registry study found that the DSS system had fewer repeat surgeries than fusion, but no differences in pain or function.

Despite their U.S. Food and Drug Administration (FDA) 510(k) clearance, which only requires showing similarity to previously approved devices and frequently does not require safety and efficacy data, these dynamic stabilization systems lack strong long-term evidence from high-quality randomized controlled trials. Most comparative studies to date have short follow-up periods and small sample sizes, and few show clear improvements in health outcomes compared to fusion with rigid devices. More rigorous research is needed to confirm whether these devices truly provide long-term benefits beyond standard treatments.

Dynamic Interspinous Process Spacer Devices and Interlaminar Spacer Devices for the Treatment of Spinal Stenosis

Spinal stenosis, or narrowing of the spinal canal or foramina due to impingement of the intervertebral disc, ligaments, and other structures, may result in progressive pain, numbness, and weakness of the legs while standing or walking. Currently, spinal decompression via laminectomy, a surgical procedure performed to increase the space between interspinous structures and to reduce neural compression, is the standard of care. Interspinous and interlaminar process spacer devices, which are inserted in between the vertebrae to expand the interspinous space, and facet joint arthroplasty, which is intended to stabilize the intervertebral joint space, have been proposed as alternative treatments of spinal stenosis.

Multiple randomized controlled trials and systematic reviews demonstrate that interspinous process devices do not yield superior long term clinical outcomes compared to standard decompression (laminectomy) for lumbar spinal stenosis including measures of pain reduction, functional improvement, or disability measures. Additionally, the use of such devices has been consistently associated with significantly higher reoperation rates. While the available data for specific devices, such as coflex^® (Companion Spine LLC, Leesburg, VA) and Superion (VertiFlex^®, San Clemente, California), demonstrate short-term improvements in some outcomes, these benefits are not consistently sustained and do not surpass those of decompression. To date, long-term data are limited, and concerns remain regarding spinous process fractures and other device-related complications. Professional guidelines, including those from the North American Spine Society, cite insufficient evidence to recommend such devices over decompression. At present, decompression remains the gold standard for surgical management of lumbar spinal stenosis. Additional comparative studies are needed to assess long-term safety, reoperation rates, and functional durability of these devices.

Functional Facet Replacement Devices

In 2023, the FDA granted premarket approval (PMA) for the Total Posterior Spine System (TOPS), a facet joint implant designed to stabilize the spine post-decompressions surgery without rigid fixation. Preliminary results from a randomized trial indicate that TOPS may provide superior outcomes to fusion at 24 months, including improved disability scores, reduced back pain, and fewer neurologic complications. However, this single study has several limitations, including short follow-up, absence of comparison to decompression alone, and incomplete outcome reporting. Long-term safety, durability, and comparative effectiveness require further investigation.

Rigid Interspinous and Interlaminar Non-Pedicle Fixation Devices

In summary, there is insufficient evidence in the peer-reviewed published medical literature to support the long-term clinical benefit of interspinous and interlaminar process fixation devices. Randomized controlled trials are needed to demonstrate the clinical utility of interspinous process fixation devices compared with established standard surgical approaches involving pedicle screw-rod fixation with lumbar fusion procedures.

Discussion

Dynamic Pedicle Screw-Associated Stabilization Devices

Isobar^™ Spinal System (Alphatec Spine, Inc. Carlsbad, CA)

Fu and colleagues (2014) conducted a study to evaluate the functional and radiological outcomes of dynamic stabilization in conjunction with spinal fusion. Prospective follow-up was conducted for 24 months on 36 participants who underwent posterior Isobar dynamic stabilization for single-level degenerative lumbar disc disease with instability (DLDI) and mild adjacent level degeneration. The authors assessed participant status with the collection of functional (visual analog scale [VAS] and Oswestry Disability Index [ODI]) and radiological data (resting, functional X-rays and MRI). At 24 months, functional outcomes demonstrated significant improvement in mean visual analog scale (VAS) score by 38.9 points (p<0.01) and ODI by 22.4 points (p<0.01). The disc height at the index and adjacent levels and intervertebral angle (IVA) at the index level showed a slight decreasing trend at each follow-up (p>0.05), while IVA at the adjacent level showed a slight increasing trend (p>0.05). Range of motion at the index level averaged 2.84° and remained unchanged at the adjacent level (p>0.05). With regard to adverse events, there were no reoperations, loosening of screws or infection reported. Two participants experienced a dural tear during the surgery and were given immediate repair. The authors concluded that individuals with single-level DLDI and mild adjacent level degeneration treated with Isobar semi-rigid stabilization demonstrated a significant improvement in functional scores 2 years postoperatively. However, disc degeneration at the adjacent and index levels appears to continue despite using semi-rigid dynamic stabilization. The authors stated that additional long-term follow-up is ongoing to provide more extensive information.

Guan and colleagues (2022) reported the results of a meta-analysis that combined data from randomized controlled trials (RCTs) and cohort studies of Isobar nonfusion and posterior lumbar interbody fusion (PLIF) for treatment of lumbar degenerative diseases. The analysis included 7 RCTs with 394 participants. The results demonstrated that Isobar nonfusion surgery reduced the surgical duration (p=0.03), decreased intraoperative bleeding (p=0.001), retained the range of motion (ROM) of surgical segment (p<0.00001) and the ROM of the lumbar spine (p<0.00001), and decreased the incidence of adjacent segment disease (ASD) (p=0.0001). However, the study did not demonstrate any significant difference in the postoperative ODI index (P=0.81), VAS score of low back pain (p=0.59), VAS score of lower limb pain (p=0.05), or Japanese Orthopaedic Association (JOA) score (p=0.27). The study had several limitations, including its small size, short follow-up time (maximum of two years), and lack of subgroup analysis. RCTs that span more than 2 years are still lacking. 

Dynesys^® Spinal System (Zimmer Biomet Inc., Warsaw, IN)

Zhou and colleagues (2023) reported the results of a meta-analysis that examined the medium and long-term clinical and radiographic outcomes of the Dynesys stabilization system compared to instrumented fusion in participants with degenerative lumbar spinal disease with or without grade I spondylolisthesis. A total of 17 studies (one RCT, 16 comparative cohort studies) and 1296 participants were included in the meta-analysis. Participants were followed for a minimum of 2 years. Clinical outcomes were measured in terms of VAS and ODI scores, screw loosening and breakage, and surgical revision. Radiographic outcomes were evaluated in terms of postoperative ROM and disc height. Additionally, adjacent segment degeneration (ASDeg) and adjacent segment disease (ASDis) were evaluated. A total of four prospective studies provided data on post-operative back pain and leg pain scores between the Dynesys and fusion groups. The combined results revealed that the postoperative VAS scores for low back pain in the Dynesys group were better than those in the fusion group. The pooled data of seven studies indicated that the Dynesys group was associated with a significantly lower rate of surgical revision than the fusion group. The pooled data of eight studies indicated that the Dynesys group showed less ASDeg than the fusion group. The pooled data of five studies revealed that the ROM at the stabilized segment in the fusion group decreased significantly more than that in the Dynesys group. Data also demonstrated that post-operative ROM in the fusion group at the proximal adjacent segment increased significantly more than in the Dynesys group. Pooled data indicated that there was not a significant difference from the fusion and Dynesys group in terms of ASDis, postoperative ODI scores, screw breakage and loosening and disc height at the surgical segment. The strength of this meta-analysis is limited by its inclusion of only one RCT, heterogeneity of measured outcomes, and relatively short follow-up times. The authors noted that screw loosening after fusion procedures is likely to occur earlier than failure of dynamic stabilization and recommended further study with follow-up longer than 10 years.

A meta-analysis of studies on the efficacy of the Dynesys system was published by Lee and colleagues in 2016. To be eligible for inclusion in the review, studies needed to compare clinical and radiological outcomes between individuals who underwent surgery with Dynesys compared to PLIF for degenerative spinal disease. A total of seven studies with 506 participants met the eligibility criteria. Of these, one was a RCT, two were prospective cohort studies and four were retrospective cohort studies. None of the studies were conducted in the U.S. Clinical and radiological outcomes, including the ODI and pain measured by a VAS, were assessed at baseline and at approximately 2 years. Pooled analyses did not find significant differences between the two surgical methods in change in the ODI or in back or leg pain VAS scores. Rates of complications and length of hospital stay were similar in the two groups. 

Several additional retrospective comparative observational studies have been published. In 2017, Wu and colleagues reported on outcomes after Dynesys stabilization (n=26) and PLIF (n=31) in individuals with lumbar degenerative disease. After a mean follow-up of 50 months (range, 46 to 65 months), there were no statistically significant differences between groups in ODI or VAS scores. Hu and colleagues (2019) published a retrospective study in individuals with multi-segmental lumbar spinal stenosis, 22 of whom were treated with Dynesys stabilization and 44 of whom had PLIF. After a minimum of 5 years of follow-up, there were no statistically significant differences in clinical outcomes (i.e., pain and function) in the two groups.

In addition to the controlled studies, a number of case series have been published (Grob, 2005; Putzier, 2005; Schaeren, 2008; Schnake, 2006; Würgler-Hauri, 2008; Zhang, 2018). A study by Welch and colleagues (2007) was conducted in the U.S. as part of a multicenter prospective FDA investigational device exemption (IDE) clinical trial. The study included 101 participants from six IDE sites who underwent dynamic stabilization with the Dynesys system. To be eligible, participants were required to have degenerative spondylolisthesis or retrolisthesis (Grade I), central or lateral spinal stenosis, and their physician’s determination that the participant required decompression and instrumented fusion for one or two contiguous spinal levels between L1 and S1. The authors reported significant improvement in mean pain and function scores from the baseline to 12-month follow-up evaluation. In addition to lack of a control group, this study had only 12 months of follow-up which is inadequate to judge safety and long-term durable outcome of the Dynesys system.

Pham and colleagues (2016) conducted a systematic review of the literature that focused on complications associated with the Dynesys stabilization system. The researchers evaluated 21 studies which included a total of 1166 participants with a mean age of 55.5 years and a mean follow-up period of 33.7 months. The data demonstrated a surgical-site infection rate of 4.3%, a pedicle screw loosening rate of 11.7%, a pedicle screw fracture rate of 1.6%, and an adjacent-segment disease (ASD) rate of 7.0%. Of studies reporting surgical revision rates, 11.3% of participants required reoperation. Of participants who developed ASD, 40.6% required a reoperation for treatment. The authors concluded that the Dynesys stabilization system has a similar complication rate compared with lumbar fusion studies and has a slightly lower incidence of ASD.

Although the Dynesys system has been in clinical use for several years, there has been only one RCT published and only a few prospective comparative studies. The available comparative studies, including the RCT, did not find that pain and function improved significantly more after undergoing Dynesys compared with PLIF. A meta-analysis of seven comparative studies also did not find a significant difference between groups in length of hospital stay or the complication rate. Thus, there is insufficient published evidence that the use of this device results in improved health outcomes compared to standard treatments.

Dynamic Soft Stabilization (DSS^TM) System (Paradigm Spine, LLC, New York, NY)

In 2018, Bieri and colleagues published an analysis of data on the Spine Tango Registry, an international registry that captures data on surgical treatment of spinal disorders. The investigators identified 202 individuals who received the DSS system and 269 individuals who underwent PLIF. Propensity-score matching was undertaken to balance groups in analysis for various patient characteristics. Matching was possible for 77 DSS-PLIF pairs. At a mean follow-up of 3 years, there was not a statistically significant difference in the mean Core Outcomes Measure Index (COMI) score improvement (3.4 points in the DSS group and 3.2 points in the PLIF group), p=0.69. Matched pairs were also similar in terms of back and leg pain relief, blood loss during surgery and complication rates. However, there were significantly fewer repeat surgeries after DSS (0.8 per 100 observed person-years) than with PLIF (2.9 per 100 observed person-years). The authors noted that there are no published prospective comparative studies evaluating the DSS system.

Regulatory Information

Several dynamic stabilization devices, including the Isobar Spinal System, the Dynesys Spinal System, the BioFlex^® (BioSpine Co., Ltd, Sungdong-gu, Seoul Korea) and the DSS^™ System have received FDA 510(k) clearance. The 510(k) review process does not involve or require extensive review of clinical trial data demonstrating the safety and efficacy of the device under review. In order to qualify for a 510(k) clearance, a manufacturer need only prove that their device is similar in function to a predicate device previously cleared or approved by the FDA. Thus, many devices cleared under this process have not yet been proven to be safe and effective based on the merits of data prospectively collected from clinical trials of the devices in question.

Dynamic Interspinous Process Spacer Devices and Interlaminar Spacer Devices

Dynamic spacer devices versus laminectomy

In a 2013 prospective, multicenter, double-blind randomized, controlled trial (RCT), Moojen compared the surgical outcomes of individuals with lumbar spinal stenosis who underwent either implantation of an interspinous process device (n=80) or spinal bony decompression (n=79). The study assessed neurogenic claudication as the primary outcome using the Zurich Claudication Questionnaire (ZCQ) score. At 8 weeks, 63% of individuals in the interspinous process device implantation group and 72% of individuals in the decompression group had a successful recovery (odds ratio [OR], 0.73; p=0.44). At 52 weeks, 66% of those in the interspinous process device implantation group and 69% of those in the decompression group (OR, 0.90; p=0.77) reported good results. While there was no significant difference between the groups in terms of long- and short-term surgical outcomes, there was a significant difference between the groups in terms of those undergoing late reoperation due to absence of recovery. In the interspinous process device implantation group, 29% (21/73) of individuals underwent reoperation compared to 8% (6/72) of individuals in the decompression group (p<0.001). The study did report shorter surgery times for the interspinous process device implantation group, but this did not translate into significantly fewer less direct complications or shorter hospital stays.

Machado performed a systematic review and meta-analysis comparing the efficacy of several surgical options to treat lumbar spinal stenosis (2015). Of the 17 randomized clinical trials included in this study, two trials compared laminectomy/laminotomies to interspinous process spacer devices (n=259). The authors reported no difference in pain reduction (moderate quality evidence). The authors also reported no difference in long-term pain, or short- or long-term disability between the groups (low quality evidence). In addition, two studies compared decompression plus fusion to interspinous process spacer devices (n=382). There was no difference in pain reduction between the groups, the interspinous spacer group did report slightly superior long-term disability outcomes (low quality evidence). The reoperation rates showed mixed results, interspinous spacers had a significantly higher rate when compared to decompression alone (34/123, 28% vs. 9/122, 7%; p<0.001), but not significantly higher when compared to decompression plus fusion (23/215, 11% vs. 8/107, 7%; p=0.36). There was no significant difference in adverse events. The authors noted that as interspinous spacers are associated with higher revision surgeries, safety of interspinous spacers in the management of individuals with lumbar spinal stenosis is questionable.

An updated systematic review by Machado (2017) included three studies which compared dynamic spacer devices to conventional decompression. The authors noted no studies directly compared spacers with decompression surgery but were based on indirect comparisons. A total of 355 individuals were included in studies for the coflex and X-Stop^® devices. The authors concluded that while surgery using the spacer devices resulted in less blood loss and shorter hospital stays when compared to fusion, use of the devices did not lead to improved outcomes when compared to decompression. In addition, spacer devices were associated with higher reoperation rates.

Wu published a systematic review and meta-analysis of two RCTs and three non-randomized prospective studies with 12 to 24 months of clinical results (2014). A total of 208 individuals received an interspinous spacer (IS) and 217 individuals received traditional decompressive surgery (TDS). Pooled analysis of four of the studies found no significant difference between the IS and TDS groups in the areas of low back pain or leg pain. In addition, there was no significant difference in Oswestry disability index (ODI) or the Roland disability questionnaire (RDQ) between the groups in the two studies which reported this outcome. There was no significant difference in complication rates between IS and TDS groups in any of the five studies. The researchers noted the incidence of reoperation was significantly lower in the TDS group (11/160, 6.9%) compared to the IS group (37/161, 23.0%) in the three studies reporting this result.

Several other systematic reviews and meta-analyses have been published. Overall, the studies reported similar results between IS devices and TDS, with the exception of higher reoperation rates in the IS groups in those that reported this outcome. At this time, additional studies are needed to further evaluate the IS device compared to the gold standard treatment of TDS (Cai, 2016; Hong, 2015; Machado, 2015; Xin, 2023).

The North American Spine Society (NASS) has two clinical guidelines that address the use of interspinous spacers in the treatment of degenerative lumbar spondylolisthesis and degenerative lumbar spinal stenosis. The NASS clinical guidelines note there is insufficient and conflicting evidence to make a recommendation for or against use of these devices for either of these conditions. In addition to the clinical guidelines, NASS also published coverage policy recommendation for interspinous devices without fusion (2014). This recommendation includes several circumstances in which static interspinous distraction devices might be appropriate. This recommendation did not include dynamic devices, such as coflex. The NASS Lumbar Spinal Stenosis Guideline Update is in development, but it is not yet a finalized replacement for the 2011 guideline (NASS, 2026).

The evidence and recommendations indicate that implanted dynamic spacers do not provide outcomes equivalent to standard decompression surgery, which remains the gold standard. More research is needed to assess reoperation rates and long-term outcomes of these devices.

The coflex Interlaminar Technology (Paradigm Spine, New York, NY)

In October 2012, the Center for Devices and Radiological Health of the FDA granted premarket approval (P110008) for commercial distribution of the coflex Interlaminar Technology implant. According to the FDA approval letter, the device is:

Indicated for use in one or two 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/buttock/groin pain, with or without back pain, and who have undergone at least 6 months of non-operative 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).

Davis (2013a) discussed the data from a clinical study to establish a reasonable assurance of the safety and effectiveness of the coflex device (IDE #G060059). A total of 322 participants were enrolled in the multi-center study (215 with coflex implantation and 107 fusion recipients). Surgeons were blinded prior to the participants being randomized and the participants were blinded until after surgery. The control group consisted of individuals who underwent posterolateral fusion with autograft bone and pedicle screw fixation following surgical decompression (D+PS). The treatment group underwent decompression and interlaminar stabilization with the coflex device (D+ILS). Participants had radiographic confirmation of moderate lumbar stenosis with narrowing of the central spinal canal at one or two contiguous levels from L1-L5 that required surgical decompression. A subset of participants with spinal stenosis had up to grade I degenerative spondylolisthesis.

Participants were scheduled to return for follow-up examinations at 6 weeks, 3 months, 6 months, 12 months, 18 months, and 24 months postoperatively. Evaluations were carried out using the ODI, ZCQ, SF-12, back and leg pain via visual analog scale (VAS). A neurological assessment was conducted during the preoperative visit and at all postoperative visits. Radiographic evaluation was performed at each time point. Adverse events and complications were recorded at all visits. With the exception of wound complications, the coflex implant was found to have a reasonable assurance of safety and to be at least as safe as the control treatment. The numerical difference of wound complications between coflex 14.0% (30/215) and control 8.4% (9/107) was 5.6%. The rate of secondary surgery (revisions and reoperations) for coflex was higher than the control group at 24 months. The study noted the presence of additional spinous process fractures in a number of participants identified by the core laboratory and not by the investigator surgeons in both the coflex and the fusion control groups. At 24 months, these fractures were asymptomatic and the evaluation of the CCS, ODI, and ZCQ endpoints for these participants did not demonstrate the clinical significance of these spinous process fractures. The long-term significance of these fractures is not known. Analysis of participant demographic and baseline data demonstrated the treatment groups to be comparable. Mean surgery time was longer for the spinal fusion group than for the coflex group. Blood loss was greater for the control group by 238.9 ml, as was length of hospital stay by 1.3 days. The results of this study suggest that the coflex interlaminar device is comparable to fusion, at least in the short term.

Musacchio (2015) reported on the 5-year outcomes of the Davis (2013a) study. Results were evaluated based upon a composite score which included four components: (1) at least 15-point improvement in the ODI (ODI-15) at 60 months compared with baseline; (2) no reoperations, revisions, removals, or supplemental fixation; (3) no major device-related complications such as permanent new or increasing sensory or motor deficit at 60 months; and (4) no lumbar epidural steroid injections within the post-operative period. At 5 years, there was no significant difference in the success rate between the D+ILS group and the D+PS group (50.3% vs. 44%; p>0.35). Specifically, at 60 months, there was no significant difference in the cumulative reoperation/revision rates between D+ILS and D+PS (35/215 [16.3%] vs. 19/107 [17.8%]; p>0.90). It is notable that this study did not include a “decompression only” group for comparison. In addition, Grade I spondylolisthesis was present in 99/215 (46.0%) of those in the coflex group and in 51/107 (47.7%) of those in the fusion group. A limitation of the study is the un-blinding of the participants postoperatively, creating the potential for expectation bias.

Davis (2013b) reported the findings of another study which evaluated a subset of the participants in the IDE trial described above (Davis 2013a). This study evaluated only the subset of individuals from this overall cohort with both lumbar spinal stenosis and Grade 1 spondylolisthesis (99 in the coflex group and 51 in the fusion group.) At a minimum of 24 months, individual follow-up was 94.9% and 94.1% in the coflex and fusion control groups, respectively. There were no group differences at baseline for any demographic, clinical, or radiographic parameter. The average age of the participants was 63 and 65 years in the coflex and fusion groups, respectively. Participants in the coflex group experienced shorter operative times (an average of 53.3 fewer minutes) than those in the fusion group. The estimated blood loss was lower for the coflex cohort (106.2 vs. 335.5 ml), and the average hospital length of stay was reduced by 1 day in the coflex group. The reoperation rate was higher in the coflex cohort (14 [14.1%] of 99) compared with fusion (3 [5.9%] of 51, p=0.18), although this difference was not statistically significant. The rate of severe adverse events that were probably or definitely related to the implant was 9.1% in the coflex arm and 7.8% in the fusion arm. Wound-related problems were seen in 14.1% of the coflex cohort compared with 13.7% in the fusion cohort. Both groups experienced significant improvements from baseline at 2 years in ODI, VAS leg and VAS back, with no significant group differences. However, coflex demonstrated significantly greater ZCQ satisfaction at 2 years. Fusion was associated with significantly greater angulation and translation at the superior and inferior adjacent levels compared with baseline, while coflex showed no significant radiographic changes at the operative or index levels.

Bae (2017) performed a 3-year follow-up analysis of the Davis (2013a) RCT. At 36 months, 91% (195/215) of the coflex group and 88% (94/107) of the fusion group were included in the analysis. The initial efficacy endpoints (composite scores) were modified for use at 36 months. At 36 months. 62.2% of the individuals in the coflex group compared to 48.9% of the individuals in the fusion group reported composite clinical success scores (difference=13.3%; 95% confidence interval [CI], 1.1%-25.5%; p=0.03). There are several limitations in this study including the limited follow-up period and the heterogeneous mix of individuals including those without listhesis. The authors noted that an RCT comparing decompression and stabilization with the coflex device to decompression alone will be underway in the near future.

In a prospective, randomized multicenter study, Schmidt (2018) reported on the 2-year results of a study comparing treatment with decompression with interlaminar stabilization with the coflex device (D+ILS) to decompression alone (DA) in individuals with moderate to severe lumbar spinal stenosis at one or two adjacent levels. A total of 115 individuals were randomized to each arm. A composite clinical success (CCS) measure consisted of four components: ODI improvement > 15 points, survivorship with no secondary surgeries or lumbar injections, maintenance or improvement of neurological symptoms, and no device- or procedure-related severe AEs. The CCS is a binary outcome measure and all components must be achieved in order for the endpoint to be met. At 24 months follow-up, the D+ILS group reported significant superior CCS scores compared to the DA group (58.4% vs. 41.7%; p=0.017 respectively). At 24 months, there were no significant differences between the groups in the participant-reported outcomes: the ODI scores, VAS back and neck pain scores and the Zürich Claudication Questionnaire. There were no significant differences in participant-reported outcomes between the groups. There were no significant differences in the primary outcome measures between the groups. However, when the secondary measure outcome of subsequent epidural injections (4.5% in the D+ILS group vs. 14.8% in the DA group) was included in the CCS, the result became significant. In a review of this study, NASS (2018) noted:

Overall, the results of this study on a strict evidence-based medicine level can be summarized as not finding a significant difference in the primary outcome measure(s). However, when considering the significant difference in subsequent epidural injections, which is a secondary outcome measure, the composite clinical success score becomes different.

Du (2020) reported on a small group of individuals who underwent interlaminar decompression and coflex implantation to treat symptomatic lumbar spinal stenosis (LSS) and completed follow-up for at least 8 years. A total of 73 individuals underwent the initial surgery and 56 individuals completed all follow-up with an average follow-up time of 107.6 ± 13.3 months. At the last follow-up, the VAS scores for leg pain, back pain and ODI were significantly improved over baseline scores. During the course of follow-up, 19.6% (10/56) reported complications and 10.7% (6/56) required a secondary surgery. While the results were promising, larger studies directly comparing decompression with the coflex device and decompression alone are needed.

In 2018, NASS published a coverage recommendation regarding the use of lumbar interspinous devices with decompression, noting that an interspinous device, the coflex device, may be used in conjunction with laminectomy. This recommendation is based upon studies comparing the coflex device/laminectomy to laminectomy alone or to fusion. The cited studies have several limitations, including short follow-up periods and a lack of clear data which directly addresses whether the coflex device provides additional benefit.

In 2022, the FDA CDRH Medical Device Material Performance Study reported 19 events of breakage and fracture that were described as definitely/probably related to coflex Interlaminar Stabilization devices:

• Breakage, spinous process fracture, loosening, and migration were reported in studies examining spinal fixation. 19 adverse events (AEs) (e.g., breakage, fracture) were described as definitely/probably related to Coflex interlaminar stabilization device.
• Spinous process fracture and adjacent segment degeneration occurred 3 months to 66 months post-Coflex interspinous device placement.

Superion^® Interspinous Spacer (Boston Scientific, Marlborough, ME) and X-STOP (Medtronic Inc., Minneapolis, MN)

The FDA granted PMA for the X-STOP interspinous implant in November 2005. The approval was contingent upon post approval follow-up data submission for safety and efficacy at 2 and 5 years. The Condition of Approval Study (COAST), a prospective Phase IV 5-year post approval study of the X-STOP device has been completed; however, results have not been published. In 2015, Medtronic noted “...study costs outweigh business benefits for marketing X-STOP in US.” and removed the device from the U.S. market.

In May 2015, the Center for Devices and Radiological Health of the FDA granted premarket approval (P140004) for commercial distribution of the Superion Interspinous Spacer (ISS). The approval was contingent upon post approval follow-up data submission for safety and efficacy at 2 and 5 years. Superion is the only non-fusion interspinous distraction device currently available in the U.S. (Guyer, 2016).

The FDA-approved indications for Superion ISS are for the treatment of neurogenic intermittent claudication symptoms caused by moderate degenerative lumbar spinal stenosis with or without Grade 1 spondylolisthesis, who have failed at least 6 months of conservative treatment. The device is approved to be implanted at one or two adjacent levels. The Superion Post-Approval Clinical Evaluation and Review (SPACER) trial has been identified as the lead PMA post approval study.

A 2014 prospective, multicenter, randomized, controlled trial by Patel evaluated surgical outcomes for individuals who received either the Superion ISS or the X-STOP implant. A total of 250 individuals with moderate lumbar spinal stenosis were followed for a minimum of 2 years post implant. While the reported indicators of successful outcomes between the groups were comparable, the study did not include a comparison to decompression surgery, the current standard surgical treatment.

The 5-year clinical outcomes of a randomized controlled FDA noninferiority trial in individuals with moderate lumbar spinal stenosis were reported by Nunley (2017). While the original trial compared the Superion to the X STOP device, the analysis was restricted to the Superion trial arm. A total of 73% (88/121) of the living individuals who received the spacer device participated in the 5-year clinical outcomes assessment. Outcomes were assessed using the ZCQ, leg and back pain severity by VAS, and the ODI. The authors reported success rates in all areas of assessment, 84% reported clinical success in at least two of the three ZCQ domains, 80% leg pain VAS scores, 65% back pain VAS scores and 65% for ODI scores. There remains a lack of studies which compare interspinous spacers to standard treatments, such as decompression surgery.

Tekmyster (2019) reported on the data captured in a post-market registry of individuals who had the Superion device placed to treat LSS associated with neurogenic claudication. The reported data included leg and back pain VAS scores and participant satisfaction at 3 weeks, 6 and 12 months. Respondents reported an overall 60% improvement in leg pain and 48% overall improvement in back pain. Scores for participant satisfaction with treatment at 3 weeks, 6 and 12 months were 89%, 80% and 80%, respectively. This observational study was limited by the low response rate and limited follow-up. The number of responders varied from 291 to 1542 out of a possible 2090 eligible individuals. In addition, the results of this study do not address concerns about long-term outcomes and clinical outcomes compared to standard decompression.

Overall, there is a lack of evidence to support that interspinous spacer devices are as safe and effective as the gold standard of decompression. Surrogate radiologic endpoint outcomes, such as improvements in spinal canal and neuroforaminal narrowing are improved following surgery. However, the studies do not show that the use of interspinous spacer devices improves clinical outcomes such as pain and function. There appears to be some concerns that the devices are not as effective as surgical decompression and lead to higher rates of reoperation.

Functional Facet Replacement Devices

Facet replacement devices is proposed as an alternative to fusion when individuals undergo decompression to treat spinal stenosis and spondylolisthesis.

Total Posterior Spine (TOPS^™) System (Premia Spine Ltd., Philadelphia, PA).

In June 2023, the FDA granted premarket approval (P220002) for commercial distribution of the TOPS System, a motion-preserving spinal implant that is inserted into the lumbar spine via pedicle screws. The device is intended to stabilize the spine following a lumbar decompression without rigid fixation. TOPS is indicated for individuals aged 35 to 80 years old with symptomatic degenerative spondylolisthesis up to Grade I, with moderate to severe lumbar spinal stenosis and either the thickening of the ligamentum flavum and/or of the scarring facet joint capsule at one level from L3 to L5.

Pinter (2023) reported interim results of the experimental group from a prospective, randomized FDA investigational device exemption (IDE) trial (TOPS FDA IDE trial) evaluating 1-year clinical safety profile and radiographic outcomes of lumbar functional facet replacement using the TOPS device (n=153). Radiographic parameters and participant-reported outcomes were assessed preoperatively and at regular postoperative intervals. The procedure showed significant improvements in ODI, VAS (leg and back), and ZCQ (p<0.001), with preserved segmental motion and no significant changes in radiographic parameters. Mean surgical time was 187.8 minutes, blood loss 205.7 cc, and hospital stay 3 days. Complications occurred in 7.2% of patients, and 5.9% underwent reoperation, with one device-related failure (0.6%). The study has several limitations; it only reports outcomes from the investigational arm of an ongoing trial, without a control group, limiting comparisons to literature-based fusion cohorts, only two-thirds of participants had reached 1-year follow-up, possibly underestimating reoperation rates, long-term complications cannot be assessed, as follow-up is under 5 years, and a small, likely insignificant decrease in lumbar lordosis was observed, but longer-term impact cannot be evaluated until 2-year data are available. The authors concluded that the final comparison of the TOPS cohort to individuals undergoing single-level TLIF at the conclusion of the ongoing clinical trial will be necessary to draw firm conclusions regarding clinical performance of the investigational TOPS device.

Corcic (2023) reported a 2 year follow up to the aforementioned TOPS FDA IDE trial. The report included a total of 321 adults randomized in a 2:1 fashion, with 219 assigned to undergo facet arthroplasty and 102 assigned to undergo fusion. Of these, 113 participants (51.6%) in the arthroplasty group and 47 (46.1%) in the fusion group who had either reached 24 months of postoperative follow-up or were deemed early clinical failures were included in the primary outcome analysis. The arthroplasty group had a higher proportion of patients who achieved composite clinical success than did the fusion group (73.5% vs. 25.5%; p<0.001), equating to a between-group difference of 47.9% (95% confidence interval, 33.0% to 62.8%). The arthroplasty group outperformed the fusion group in most outcome measures (including the ODI, VAS back pain, and all ZCQ component scores) at 24 months postoperatively. There were no significant differences between groups in surgical variables or complications, except that the fusion group had a higher rate of developing symptomatic adjacent segment degeneration. The authors concluded that in individuals with lumbar spinal stenosis and grade-I degenerative spondylolisthesis, functional lumbar facet replacement was associated with a higher rate of composite clinical success than fusion was at 24 months postoperatively. Study limitations included the short follow-up period, lack of blinding, strict inclusion/exclusion criteria which limits generalizability, and the use of radiographs instead of CT to assess fusion. Additionally, the primary outcomes were reported for only half the sample. The authors concluded decompression plus functional lumbar facet replacement showed superior outcomes, fewer neurologic complications, and lower rates of adjacent segment degeneration compared to decompression with fusion, resulting in higher composite clinical success. While the results are promising, long-term follow-up is needed to assess implant longevity, sustained motion, and spondylolisthesis stability. Additional long-term comparative RCTs with decompression alone in a broader population are needed to determine whether implanted facet replacement devices achieve outcomes equivalent to standard surgical approaches and to evaluate reoperation rates and long-term durability.

Rigid Interspinous and Interlaminar Non-Pedicle Fixation Devices

The standard surgical procedure for rigid spinal fixation involves the use of pedicle screws and rods. Non-pedicle interspinous process and interlaminar fixation devices (with or without additional instrumentation) were developed as a minimally invasive rigid fixation alternative to standard rigid fixation instrumentation using pedicle screws and rods or interbody cages. According to the FDA 510(k) clearance, these fixation devices are intended for use with bone graft material and are not intended for stand-alone use.

Available evidence comparing the Aspen^® Spinous Process Fixation System (Highridge Medical, Westminster, Colorado) to standard pedicle fixation includes two articles describing the biomechanical effect of the device on cadaver spines (Kaibara, 2012; Karahalios, 2010) and a small prospective study evaluating individuals with a primary diagnosis of lumbar spinal stenosis (with pain) treated with the Aspen device or an interspinous process spacer (Kim, 2012a). Of the 6 individuals implanted with the Aspen device (as a stand-alone procedure), 2 (33%) had postoperative spinous process fractures observed on computed tomography (CT). Limitations of this study include lack of randomization and small sample size leading to insufficient power to detect risk factors for fracture or differences in patient-centered outcomes.

Kim and colleagues (2012b) retrospectively compared 40 individuals who underwent single level spinal fusion with the CD HORIZON^® SPIRE™ (Medtronic Sofamor Danek, Inc., U.S.A., Memphis, TN) interspinous fusion device (IFD) for lumbar spine disease (n=12, degenerative spondylolisthesis; n=2, intervertebral disc herniation; n=26, spinal stenosis) to 36 individuals with similar lumbar spinal disorders (n=10, degenerative spondylolisthesis; n=7, foraminal stenosis; n=1, intervertebral disc herniation; n=18, spinal stenosis) who underwent spinal fusion with pedicle screw fixation. All individuals in both groups underwent posterior lumbar interbody fusion with a polyetheretherketone cage or a titanium alloy cage. Both groups were evaluated using dynamic lateral radiographs, visual analogue scale (VAS), and a Korean version of the Oswestry Disability Index (K-ODI) scores. The mean follow-up period was 14.2 months in the IFD group and 18.3 months in the pedicle screw group. At 1-year follow-up, there was an improvement in the mean preoperative to postoperative VAS scores from 7.16 (± 2.1) to 1.3 (± 2.9) and 8.03 (± 2.3) to 1.2 (± 3.2) (p<0.05) in the IFD and pedicle screw groups, respectively. The K-ODI was reduced significantly in an equal amount in both groups 1 year postoperatively (p<0.05); however, no statistical difference in clinical outcomes was noticed between the 2 groups. Postoperative radiographs in the IFD group showed less improvement of instability at the instrumented level compared with the pedicle screw group. A higher incidence of adjacent segmental degeneration was reported in the pedicle screw group (n=13, 36.1%) than in the IFD group (n=5, 12.5%; p=0.029). In the IFD group, 1 individual had sustained back pain, and lumbar CT revealed fusion failure and inferior articular process fracture. There were no major surgery-related complications such as deep infection, nerve root injury, and cerebral spinal fluid (CSF) leakage in the IFD group; however, in the pedicle screw group, 3 individuals developed deep infection, 2 individuals experienced CSF leakage, and 1 individual required re-operation for a postoperative epidural hematoma. Limitations of this study include the retrospective, nonrandomized design, the heterogeneous population of participants in terms of preoperative diagnoses, and a relatively short-term follow-up period.

Sclafani and colleagues (2014) retrospectively reviewed medical records to evaluate postoperative clinical outcomes in 53 individuals who were implanted with a second generation polyaxial PrimaLOK™ SP Interspinous Fusion System (OsteoMed, Addison, TX). All participants reached the 1-year postoperative time point. Participants had a mean age of 60 years (range, 34-89 years) at the time of surgery. The most common primary surgical indications were degenerative disc disease with stenosis (45.3%), herniated disc (18.9%) and spondylolisthesis (11.3%). A total of 34 participants were implanted with the PrimaLOK SP device, 16 participants received both a polyetheretherketone interbody cage and the PrimaLOK SP device, and 3 participants received pedicle screw instrumentation, a polyetheretherketone interbody cage and the PrimaLOK SP device. Complications included intraoperative dural tear (n=1) and readmission for intractable pain after a post-discharge mechanical fall (n=1). There were no cases of fracture or migration of the device observed at the 6-week postoperative time point; however, there were 4 cases of hardware removal and 2 cases of re-operation for adjacent level disease during the follow-up period. The pain index score improved from 7.17 ± 1.68 to 4.48 ± 2.8 (p=0.0001, 22 months average follow-up) for the overall study group. There was no difference in Macnab classification score between different primary surgical indication groups (χ² p>0.05). Limitations of this review include the retrospective study design and lack of data collection on preoperative VAS scores of low back and leg pain and validated quality of life of life data to distinguish if the postoperative improvement was predominantly in axial low back pain, radicular lower extremity pain or neurogenic claudication.

Lopez and colleagues (2017) systematically evaluated the literature on lumbar spinous process fixation and fusion devices (excluding dynamic fixation and spinous process spacer devices). A total of 15 articles met the inclusion and exclusion criteria, including 4 comparative studies (level III evidence), 2 case series (level IV evidence), and 9 in vitro biomechanics studies (level V evidence). Two of the nonrandomized studies compared interspinous process fixation devices to pedicle screws in individuals undergoing interbody fusion and two other studies included interspinous process fixation devices alone or pedicle screws plus an interspinous process fixation device in individuals undergoing interbody fusion. Use of an interspinous process fixation device was associated with decreased surgical time and blood loss compared to pedicle screw implantation procedures. The authors reported that flawed study designs may have inadequately controlled for biases when reporting outcomes of reduced spinal instability at 1 year, rates of device failure, bony fracture, and complications. No comparative studies exist that report either complication rates of interspinous process fixation devices to other treatment modalities or length of hospital stay for interspinous process fixation devices compared to pedicle screw implantation procedures.

In 2019, Wei and colleagues published the results of a retrospective study that included 95 participants with lumbar disc herniation (LDH). The participants were treated with inter-spinal distraction fusion (ISDF) using the BacFuse^® Spinous Process Fusion Plate (RTI Surgical, Inc., Marquette, MI). Symptoms and imaging were evaluated prior to surgery, immediately following surgery, 6 months post-op, and a single final visit (average was 15.4 ± 3.4 months). Follow-up assessment reported improvements from baseline in VAS from 6.7 ± 1.3 to 2.1 ± 1.4 (p<0.001) at final follow-up, and ODI of 33.3 ± 6.2 to 12.5 ± 5.7 (p<0.001) at final follow-up. Imaging showed the anterior disc height was not statistically different at the post-operative follow-up (p=0.502). The imaging results showed initial improvement in imaging for both posterior disc height (18.3%) and foraminal height (9.7%), only to have decreases of 2.4% and 5.1% respectively, at the final follow-up. Only 1 participant suffered a spinous process fracture but this did not cause significant back discomfort and was treated non-operatively. Long-term studies with a robust sample size are needed to show the product is durable and participants experience long-term improvement with use of the BacFuse implant for LDH.

A 2023 prospective study by Skoblar and colleagues evaluated radiographic fusion outcomes of individuals who received a minimally invasive interspinous fixation device. This was a single-center, single-physician study in which 43 individuals returned to the surgeon’s office for a follow-up computed tomography (CT) scan to assess the fusion. Follow-up was done at a mean of 459 days following surgery. Of the levels assessed, 92.8% were considered fused by CT scan. CT imaging identified four spinous process fractures which were asymptomatic and healed without intervention. In this study, there were no clinical outcomes provided, nor was there comparison to a control group.

In 2024, Baranidharan reported the two-year results of a multi-center, prospective, randomized controlled trial (RCT) which compared the efficacy of an implanted interspinous fixation device (the Minuteman^® interspinous fixation device) to open direct surgical decompression for treatment of lumbar spinal stenosis. Efficacy was assessed using the VAS for leg and back pain, ODI for pain-related disability, the physical function component of the Zurich Claudication Questionnaire (ZCQ) for lumbar spinal stenosis physical function, the functional status questionnaire for activities of daily living (ADL), analgesic and concomitant medication use and employment status. Physical function was also assessed using a walking distance test (distance walked in five minutes) and a sitting-to- standing test (number of repetitions completed from sitting to standing in one minute). Participants were randomized in a 1:1 fashion between interspinous fixation (n=20) and decompression (n=23). Prior to surgery, there were 2 participants who instead of receiving interspinous fixation had decompression surgery instead. At 24 months, there were 15 (75%) fixation device participants available for follow-up and 19 (83%) decompression participants available. Clinical success was defined as a greater than or equal to 30% improvement in leg pain (as measured by VAS), back pain (as measured by VAS), pain-related disability (as measured by ODI), and greater than 0.5-point improvement in lumbar spinal stenosis function (as measured by ZCQ). There were three decompression cases and one interspinous fixation case which did not have a favorable outcome throughout the 24-month post-surgical period. There were an additional five participants who showed a loss of clinical benefit at the 24-month follow-up (three cases were interspinous fixation and 2 cases were decompression surgery). At the 24-month visit, the clinical success rate for leg pain in the interspinous fixation device group was noted in 72% of participants and for back pain success was noted in 56% of participants. The clinical success rates for leg pain for those in the decompression group at 24 weeks was 76% and for back pain was also 76%. The clinical success rates for ODI disability for those who had interspinous fixation devices were 56% at 24 months and was 80% for those who had decompression surgery. There were 50% of participants who had clinical success rates after interspinous fixation device surgery for the ZCQ and 80% in the decompression group. The mean increase in walking distance varied between 66% and 94% in the interspinous fixation device cohort and varied between 34% and 53% for those in the decompression group. For the sitting-to-standing repetitions, the mean increase was larger in the interspinous fixation device group compared to the decompression group but was not statistically significant (0.105 < 0.972). The authors noted at least two study investigators deviated from the randomization assignments which lowered the sample size in the interspinous fixation device group which failed to establish noninferiority of the interspinous fixation device relative to decompression surgery.

In 2025, the North American Spine Society (NASS) issued coverage recommendations for interspinous fixation devices noting:

There has been an increasing body of published literature on outcomes related to interspinous devices which affix to the spinous processes for the purposes of augmenting fusion. There is still limited evidence published about outcomes of such devices that are used for stabilization of a motion segment, but the evidence has improved with regards to the quality of studies that support this technique. There are published prospective studies that support the use of this technology for stabilization of single-level degenerative spondylolisthesis when combined with a direct decompression and fusion. Trials comparing interspinous fixation (ISF) to PS are limited due to small sample size and methodological uncertainties but suggest similar clinical outcomes when either is performed as a supplement to interbody fusion. However, there is some evidence that interspinous devices which affix to the spinous processes may be less mechanically stabilizing than PS constructs. Overall, there are insufficient prospective randomized trials with sufficient follow-up to determine the relative effectiveness and safety of this class of devices in comparison to PS fixation.

Dynamic Pedicle Screw-Associated Stabilization Devices

Spondylolisthesis is a condition in which a backbone (vertebra) slips forward on the vertebra below it. In adults, the most common cause is degenerative arthritis involving the fourth and fifth lumbar vertebrae. Other causes of spondylolisthesis include, but are not limited to, spinal fracture, and bone disease. Symptoms may include lower back pain and pain in the thighs and buttocks, stiffness, muscle tightness, and spinal tenderness. Neurologic damage (leg weakness or sensory changes) may result from pressure on nerve roots and may cause pain radiating down the legs.

Treatment varies depending on the severity of the spondylolisthesis. Most individuals require only strengthening and stretching exercises combined with activity modification (for example, avoiding hyperextension of the back and contact sports).

For cases with severe pain not responding to therapy, if the slip is severe, or there are neurologic changes (loss of feeling in the legs, etc.), the slipping vertebra might be surgically fused to adjacent vertebrae to prevent further slippage and provide relief of symptoms.

Fusion procedures may involve placement of a bone graft or equivalent substance between the vertebrae after removal of the intervertebral disc as well as attachment of a rigid metal frame to adjacent vertebral bodies. The frame is used to hold the adjacent vertebrae in place while the joint spaces fuse over time. As a result of fusion surgery, there is a subsequent loss of mobility where the intervertebral and facet joints once were. This loss of mobility has been associated with increased loading on adjacent joints and potential complications related to failure of those joints.

In an attempt to overcome the disadvantages of rigid instrumentation and improve the outcome of spinal fusion surgery, dynamic stabilization devices have been proposed as an alternative to the use of standard rigid frames. Like standard frame devices, these devices are fixed in place using pedicle screws which are attached to the vertebral bodies being fused. Unlike standard frames, these devices are designed using flexible materials which purport to stabilize the joint while still providing some measure of flexibility.

Dynamic Interspinous Process Spacer Devices and Interlaminar Spacer Devices

Spinal stenosis or narrowing of the spinal canal may cause neurogenic intermittent claudication, a syndrome that individuals may experience as progressive pain, numbness, and weakness of the legs while standing or walking. Currently, spinal stenosis can be treated by laminectomy, a surgical procedure performed to increase the space between interspinous structures and to reduce neural compression. The risks associated with laminectomy are nerve damage, vertebral instability, and return of symptoms at another level of the spine. Neurogenic intermittent claudication (NIC) secondary to LSS is a bio-mechanical, posture-dependent condition in which symptoms such as lower limb tingling, pain, and numbness are typically exacerbated in extension and relieved in flexion. The central canal, lateral recess or intervertebral foramen are the usual sources of stenotic changes and nerve impingement (Truumees, 2005). Spinal stenosis is a progressive disease and while decompression surgery is used to treat the symptoms of spinal stenosis, symptoms can recur (Schmidt, 2018).

Decompression, with or without fusion, is currently the gold standard for the surgical treatment of stenosis. The placement of an dynamic spacer device following decompression has been proposed as an alternative to fusion. The device is meant to provide segmental stability while avoiding limitations associated with fusion, such as motion limitation or adjacent segment degeneration. The coflex device is the only device with FDA PMA approval for this use. The use of stand-alone interspinous distraction devices is also proposed as an alternative to decompression. At present, the Superion device is the only FDA approved non-fusion interspinous distraction device available.

Rigid Interspinous and Interlaminar Non-Pedicle Fixation Devices

The pedicles are two short, thick bridges of bone that connect the front of a vertebra to the back of the vertebra. They help form the protective ring of bone around the spinal cord and provide a strong anchor point for the back of the spine. The laminae are two flat plates of bone that extend from the pedicles and meet in the middle of the back to form the roof of the spinal canal. Together, the pedicles and laminae create a bony arch that surrounds and protects the spinal cord and spinal nerves. One type of fixation involves pedicle screws that are inserted as anchors for rods that provide fixation. Another type of fixation is an interbody cage placed in the disc space. Both of these fixation devices support fusion and are typically used with bone graft material.

Rigid interspinous and interlaminar non-pedicle fixation devices attach to a vertebral spinous process or the lamina and are intended for use as an adjunct to or an alternative to traditional instrumented fusion procedures.

Foramen: Space between adjacent vertebrae through which the nerve root exits at each level in the spine.

Investigational Device Exemption (IDE): Allows the investigational device to be used in a clinical study in order to collect safety and effectiveness data required to support a Premarket Approval (PMA) application or a Premarket Notification [510(k)] submission to FDA.

Lamina: Part of the vertebra located behind the vertebral body. A flat area of bone between the superior process forming the facet joint and the spinous process, helping to form the central canal through which the spinal cord passes.

Laminectomy: Also known as decompression. A surgical procedure for treating spinal stenosis by relieving pressure on the spinal cord. The lamina of the vertebra is removed or trimmed to widen the spinal canal and create more space for the spinal nerves.

Neurogenic: Originating in the nervous system.

Neurogenic claudication: Symptoms of leg pain (and occasionally weakness) on walking or standing, relieved by sitting or spinal flexion, related to neural compression, usually spinal stenosis.

Pedicles: Two short, thick bony processes with a dense cortical shell that project posteriorly from the posterolateral aspect of the vertebral body. Together with the laminae, they form the vertebral arch, which surrounds and protects the spinal cord.

Premarket Approval (PMA): The most stringent type of device marketing application required by the FDA. A PMA is an application submitted to the FDA to request clearance to market or to continue marketing of a Class III medical device. Class III medical devices are those devices that present significant risk to the individual and/or require significant scientific review of the safety and effectiveness of the medical device prior to commercial introduction. Frequently the FDA requires follow-up studies for these devices.

Spinal fusion: A surgical procedure to stabilize the spine by fusing together two or more vertebrae.

Spinous process: The small, bony protuberances located along the back of the spinal column that act as attachment sites for muscles and ligaments.

Spondylolisthesis: A condition that occurs when one vertebra slips out of the proper position onto the bone below it.

Spondylolysis: A condition where there is a defect in a specific region of the spinal column. This region of the spinal column, called the pars interarticularis, connects adjacent vertebrae in the spine.

Vertebrae: Bones that make up the spinal column, which surround and protect the spinal cord.

The following codes for treatments and procedures applicable to this document are included below for informational purposes. Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy. Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

When services are Investigational and Not Medically Necessary:
For the following procedure codes, or when the code describes a procedure indicated in the Position Statement section as investigational and not medically necessary.

Associated Coding

When services are also Investigational and Not Medically Necessary for associated add-on codes related to primary procedure codes listed above:

Peer Reviewed Publications:

1. Anderson PA, Tribus CB, Kitchel SH. Treatment of neurogenic claudication by interspinous decompression: application of the X STOP device in patients with lumbar degenerative spondylolisthesis. J Neurosurg Spine. 2006; 4(6):463-471.
2. Bae HW, Davis RJ, Lauryssen C, et al. Three-year follow-up of the prospective, randomized, controlled trial of coflex interlaminar stabilization vs instrumented fusion in patients with lumbar stenosis. Neurosurgery. 2016; 79(2):169-181.
3. Bae HW, Lauryssen C, Maislin G, et al. Therapeutic sustainability and durability of coflex interlaminar stabilization after decompression for lumbar spinal stenosis: a four year assessment. Int J Spine Surg. 2015; 9:15.
4. Baranidharan G, Bretherton B, Feltbower RG, et al. 24-month outcomes of indirect decompression using a minimally invasive interspinous fixation device versus standard open direct decompression for lumbar spinal stenosis: a prospective comparison. J Pain Res. 2024; 17:2079-2097.
5. Bieri KS, Goodwin K, Aghayev E, et al Dynamic posterior stabilization versus posterior lumbar intervertebral fusion: a matched cohort study based on the Spine Tango Registry. J Neurol Surg; 2018; 79:224-230.
6. Cai Y, Luo J, Huang J, et al. Interspinous spacers versus posterior lumbar interbody fusion for degenerative lumbar spinal diseases: a meta-analysis of prospective studies. Int Orthop. 2016; 40(6):1135-1142.
7. Christie SD, Song JK, Fessler RG. Dynamic interspinous process technology. Spine. 2005; 30(16 Suppl):S73-S78.
8. Coric D, Nassr A, Kim PK, et al. Prospective, randomized controlled multicenter study of posterior lumbar facet arthroplasty for the treatment of spondylolisthesis. J Neurosurg Spine. 2022; 38(1):115-125.
9. Davis R, Auerbach JD, Bae H, Errico TJ. Can low-grade spondylolisthesis be effectively treated by either coflex interlaminar stabilization or laminectomy and posterior spinal fusion? Two-year clinical and radiographic results from the randomized, prospective, multicenter US investigational device exemption trial: clinical article. J Neurosurg Spine. 2013b; 19(2):174-184.
10. Davis RJ, Errico TJ, Bae H, Auerbach JD. Decompression and coflex interlaminar stabilization compared with decompression and instrumented spinal fusion for spinal stenosis and low-grade degenerative spondylolisthesis: two-year results from the prospective, randomized, multicenter, food and drug administration investigational device exemption trial. Spine. 2013a; 38(18):1529-1539.
11. de Kleuver M, Oner FC, Jacobs WC. Total disc replacement for chronic low back pain: background and a systematic review of the literature. Eur Spine J. 2003; 12(2):108-116.
12. Du MR, Wei FL, Zhu KL, et al. Coflex interspinous process dynamic stabilization for lumbar spinal stenosis: Long-term follow-up. J Clin Neurosci. 2020; 81:462-468.
13. Fiani B, Noblett C, Chacon D, et al. Total posterior spinal arthroplasty systems for dynamic stability. Cureus. 2020; 12(12):e12361.
14. Fu L, France A, Xie Y, et al. Functional and radiological outcomes of semi-rigid dynamic lumbar stabilization adjacent to single-level fusion after 2 years. Arch Orthop Trauma Surg. 2014; 134(5):605-610.
15. Gala RJ, Russo GS, Whang PG. Interspinous implants to treat spinal stenosis. Curr Rev Musculoskelet Med. 2017; 10(2):182-188.
16. Grob D, Benini A, Junge A, Mannion AF. Clinical experience with the Dynesys semirigid fixation system for the lumbar spine: surgical and patient-oriented outcome in 50 cases after an average of 2 years. Spine. 2005; 30(3):324-331.
17. Guan J, Liu T, Li W, et al. Effects of posterior lumbar nonfusion surgery with isobar devices versus posterior lumbar interbody fusion surgery on clinical and radiological features in patients with lumbar degenerative diseases: a meta-analysis. J Orthop Surg Res. 2022; 17(1):116.
18. Hong P, Liu Y, Li H. Comparison of the efficacy and safety between interspinous process distraction device and open decompression surgery in treating lumbar spinal stenosis: a meta analysis. J Invest Surg. 2015; 28(1):40-49.
19. Hsu KY, Zucherman JF, Hartjen CA, et al. Quality of life of lumbar stenosis-treated patients in whom the X STOP interspinous device was implanted. J Neurosurg Spine. 2006; (6):500-507.
20. Hu A, Sun C, Liang Y, et al. Multi-segmental lumbar spinal stenosis treated with Dynesys stabilization versus lumbar fusion in elderly patients: a retrospective study with a minimum of 5 years' follow-up. Arch Orthop Trauma Surg. 2019; 139(10):1361-1368.
21. Huang WM, Yu XM, Xu XD, et al. Posterior lumbar interbody fusion with interspinous fastener provides comparable clinical outcome and fusion rate to pedicle screws. Orthop Surg. 2017; 9(2):198-205.
22. Kaibara T, Karahalios DG, Porter RW, et al. Biomechanics of a lumbar interspinous anchor with transforaminal lumbar interbody fixation. World Neurosurg. 2010; 73(5):572-577.
23. Karahalios DG, Kaibara T, Porter RW, et al. Biomechanics of a lumbar interspinous anchor with anterior lumbar interbody fusion. J Neurosurg Spine. 2010; 12(4):372-380.
24. Kim DH, Shanti N, Tantorski ME, et al. Association between degenerative spondylolisthesis and spinous process fracture after interspinous process spacer surgery. Spine J. 2012a; 12(6):466-472.
25. Kim DH, Tantorski M, Shaw J, et al. Occult spinous process fractures associated with interspinous process spacers. Spine (Phila Pa 1976). 2011; 36(16):E1080-1085.
26. Kim HJ, Bak KH, Chun HJ, et al. Posterior interspinous fusion device for one-level fusion in degenerative lumbar spine disease: comparison with pedicle screw fixation - preliminary report of at least one year follow up. J Korean Neurosurg Soc. 2012b; 52(4):359-364.
27. Kondrashov DG, Hannibal M, Hsu KY, Zucherman JF. Interspinous process decompression with the X STOP device for lumbar spinal stenosis: a 4-year follow-up study. J Spinal Disord Tech. 2006; 19(5):323-327.
28. Lee C-H, Jahng T-A, Hyun S-J, et al. Dynamic stabilization using the Dynesys system versus posterior lumbar interbody fusion for the treatment of degenerative lumbar spinal disease; a clinical and radiological outcomes-based meta-analysis. Neurosurg Focus 2016; 40:1-9.
29. Lee J, Hida K, Seki T, et al. An interspinous process distractor (X STOP) for lumbar spinal stenosis in elderly patients: preliminary experiences in 10 consecutive cases. J Spinal Disord Tech. 2004; 17(1):72-77.
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Government Agency, Medical Society, and Other Authoritative Publications:

1. Deer TR, Grider JS, Pope JE, et al. Best practices for minimally invasive lumbar spinal stenosis treatment 2.0 (MIST): consensus guidance from the American Society of Pain and Neuroscience (ASPN). J Pain Res. 2022; 15:1325-1354.
2. Guyer R, Musacchio M, Cammisa FP Jr, Lorio MP. ISASS recommendations/coverage criteria for decompression with interlaminar stabilization - coverage indications, limitations, and/or medical necessity. Int J Spine Surg. 2016; 10:41.
3. Kreiner DS, Shaffer WO, Baisden JL, et al.; North American Spine Society. An evidence-based clinical guideline for the diagnosis and treatment of degenerative lumbar spinal stenosis (update). Spine J. 2013; 13(7):734-743.
4. Machado GC, Ferreira PH, Yoo RI, et al. Surgical options for lumbar spinal stenosis. Cochrane Database Syst Rev. 2016;(11):CD012421.
5. North American Spine Society (NASS). Clinical Guidelines for Multidisciplinary Spine Care: Diagnosis and treatment of degenerative lumbar spondylolisthesis. Revised 2014. Available at: https://www.spine.org/Portals/0/Documents/ResearchClinicalCare/Guidelines/Spondylolisthesis.pdf. Accessed on June 26, 2026.
6. North American Spine Society (NASS). Coverage Policy Recommendations. Available at: https://www.spine.org/coverage#:~:text=The%20North%20American%20Spine%20Society%20Coverage%20Recommendations%20are%20developed%20to,expert%20opinion%20of%20committee%20members. Accessed on August 12, 2026.
   • Interspinous Device without Fusion and without Decompression. Revised March 2025.
   • Interspinous Device with Decompression. Revised March 2025.
   • Interspinous Devices for Fusion Revised. March 2025.
7. North American Spine Society (NASS). Lumbar Spinal Stenosis Guideline Development - Key/PICO Questions Public Comment Period. June 16, 2026. Available at: https://www.spine.org/Publications/NASS-Insider/Details?articleid=%7bCD1B0B09-5968-F111-A826-7C1E5202050A%7d. Accessed on August 12, 2026.
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9. U.S. Food and Drug Administration (FDA) Center for Devices and Radiological Health. New device approval letter. June 3, 2015. Superion InterSpinous Spacer (ISS). P140004. Available at: http://www.accessdata.fda.gov/cdrh_docs/pdf14/P140004a.pdf. Accessed on August 12, 2026.
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1. American Academy of Orthopaedic Surgeons (AAOS). Lumbar spinal stenosis. Last reviewed: August 2021. Available at: https://orthoinfo.aaos.org/en/diseases--conditions/lumbar-spinal-stenosis/#:~:text=This%20procedure%20involves%20removing%20the,incision%20to%20access%20your%20spine. Accessed on August 12, 2026.
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4. National Library of Medicine. Medline Plus. Medical encyclopedia. spinal fusion. Last reviewed: September 2, 2025. Available at: https://medlineplus.gov/ency/article/002968.htm. Accessed on August 12, 2026.

ACADIA^® Facet Replacement System
Aileron^® Interspinous Fixation System
Aurora Spine ZIP™ MIS Interspinous Fusion System
Axle™ Interspinous Fusion System
BioFlex System
BridgePoint™ Spinous Process Fixation System
CD HORIZON™ Spinal Fixation System
coflex
coflex-F^® Implant System
Dynabolt Dynamic Stabilization System
Dynamic Interlaminar Spacer Devices
Dynamic Interspinous Process Spacer Devices
Dynamic Pedicle Screw-Associated Stabilization Devices
Dynamic Soft Stabilization System (DSS)
Dynamic Stabilization
Dynesys Spinal System
Functional Facet Replacement Devices
Implanted Devices for Spinal Stenosis
Interspinous Implant
Interspinous Process Fexation Devices
Intervertebral Stabilization Devices
Isobar Spinal System
Minuteman G3 Interspinous Interlaminar Fusion Device
Motion Preserving Stabilization Systems
PrimaLOK SP Interspinous Fusion System
Rigid Interlaminar Non-pedicle Fixation Devices
Rigid Interspinous Non-pedicle Fixation Devices
Rigid Stabilization Systems
SP-Fix^® Spinous Process Fixation Plate
Spondylolisthesis
Stabilimax NZ Dynamic Spine Stabilization System
StabiLink^® MIS Interspinous Fixation System
Superion Interspinous Spacer (ISS)
Total Posterior Spine (TOPS) System
VertiFlex

The use of specific product names is illustrative only. It is not intended to be a recommendation of one product over another, and is not intended to represent a complete listing of all products available.

Federal and State law, as well as contract language, including definitions and specific contract provisions/exclusions, take precedence over Medical Policy and must be considered first in determining eligibility for coverage. The member’s contract benefits in effect on the date that services are rendered must be used. Medical Policy, which addresses medical efficacy, should be considered before utilizing medical opinion in adjudication. Medical technology is constantly evolving, and we reserve the right to review and update Medical Policy periodically.

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