Surgery Section - Interspinous Distraction Devices (Spacers)

IMPORTANT REMINDER

This Medical Policy has been developed through consideration of medical necessity, generally accepted standards of medical practice, and review of medical literature and government approval status.

Benefit determinations should be based in all cases on the applicable contract language. To the extent there are any conflicts between these guidelines and the contract language, the contract language will control.

The purpose of medical policy is to provide a guide to coverage. Medical Policy is not intended to dictate to providers how to practice medicine. Providers are expected to exercise their medical judgment in providing the most appropriate care.

Description

Surgical decompression with or without fusion is the standard surgical treatment for patients with moderate to severe lumbar spinal stenosis.  Lumbar interspinous process decompression (IPD), also known as interspinous distraction or posterior spinal distraction, has been proposed as a minimally invasive alternative to laminectomy and fusion.  In IPD an interspinous distraction implant, also called a spacer, is inserted between the spinous processes through a small (4–8 cm) incision. The supraspinous ligament is maintained and assists in holding the implant in place. No laminotomy, laminectomy or foraminotomy is performed. The device is intended to restrict painful motion while enabling otherwise normal motion. The device theoretically enlarges the neural foramen, decompresses the cauda equina and acts as a spacer between the spinous processes to maintain the flexion of the spinal interspace.

Several IPD deviceshave been investigated (e.g., X STOP®, Wallis®, Minns, Coflex™ (formerly Intraspinous U), DIAM™, BioFLex System with Nitinol implants). The X STOP Interspinous Process Decompression System (Kyphon, Inc., St. Francis Medical Technologies, Inc.) is the only IPD system that has received clearance from the U.S. Food and Drug Administration (FDA). The FDA-labeled indication for the device is treatment of patients aged 50 or older suffering from neurogenic intermittent claudication secondary to a confirmed diagnosis of lumbar spinal stenosis with X-Ray, MRI or CT evidence of thickened ligamentum flavum, narrowed lateral recess and/or central canal narrowing.  The X STOP® is indicated for those patients with moderately impaired physical function who experience relief in flexion from their symptoms of leg/buttock/groin pain with or without back pain and have undergone a regimen of at least six months of nonoperative treatment.  The device is approved for implantation at one or two lumbar levels in patients in whom operative treatment is indicated at no more than two levels.

The Wallis® System (Abbott Spine) was introduced in Europe in 1986. The first generation Wallis® implant was a titanium block, the second generation device is composed of a plastic-like polymer that is inserted between adjacent processes and held in place with a flat cord that is wrapped around the upper and lower spinous processes. The Wallis® System is currently being tested in a FDA-regulated clinical trial. Also in a FDA-regulated clinical trial is the DIAM™ Spinal Stabilization System (Medtronic Sofamor Danek), which is a soft interspinous spacer with a silicone core. The DIAM system requires removal of the interspinous ligament and is secured with laces around the upper and lower spinous processes.  The Coflex™ implant (Paradigm Spine) and the ExtendSure and CoRoent (both from NuVasive) are used in Europe but are not currently FDA approved.

Proponents of IPD list the advantages of IPD compared with standard surgical decompression techniques to be the option of local anesthesia, shorter hospital stay and rehabilitation period, preservation of local bone and soft tissue, reduced risk of epidural scarring and cerebrospinal fluid leakage and reversibility that does not limit any future treatment options. The potential complications of IPD are implant dislodgement, incorrect positioning of implant, fracture of the spinous process, foreign body reaction (e.g., allergic reaction to titanium alloy) and mechanical failure of the implant.

Note: This policy considers only IPD devices.  Dynamic stabilization devices across pedicle screws are considered separately in Regence policy Surgery No.143, Lumbar Dynamic Stabilization.

Policy/Criteria

Interspinous process decompression devices are considered investigational for all indications.

Scientific Background

In accordance with recognized evidence-based methodology, assessing the literature related to IPD includes several considerations.  When assessing the efficacy of treatment of low back pain, randomized placebo-controlled trials are considered particularly important to control not only for the expected placebo effect, but to also control for the variable natural history of low back pain which may resolve with conservative treatment alone. In addition, the assessment of the durability of surgical treatment for lumbar spinal disorders requires long-term follow-up data since the results of lumbar surgeries are known to deteriorate over time.  Finally, since many of the advantages of IPD are related to minimal invasiveness compared to laminectomy with or without fusion, it would be helpful in determining efficacy to have clinical trial data comparing these surgeries.

There are currently no long-term clinical trials for IPD.  Nor are there any clinical trials comparing IPD with sham IPD or with laminectomy with or without fusion.  The published clinical trial data are relatively sparse and consist largely of small, non-randomized, uncontrolled studies with short-term follow-up comparing IPD with conservative medical management. For example, Lee and colleagues reported the results of X STOP® implantation in ten consecutive patients, nine single-level and one double-level.  (2) The mean period of follow-up was 11 months (range 9-18) following surgery. The authors reported that 70% of the patients were at least somewhat satisfied with the outcome of their surgery. Objective measures were also provided (e.g., foramen size). The authors concluded that the minimally invasive nature of X STOP® implantation was favorable when compared to decompressive surgery.  However, this study suffers from the design flaws noted above and does not permit scientific conclusions.  Siddiqui and colleagues reported on changes in MRI measurements in twelve patients prior to and six months following insertion of the X STOP® device.  (3) Patient specific outcomes were not reported.  Measurements for dural sac area and intervertebral forminal area showed a significant postoperative increase of 20% and 30%, respectively.  Disc height was also significantly increased. In another industry-sponsored trial by the same primary author, the neural foramina and spinal canal area were examined in 26 patients with spinal stenosis and neurogenic intermittent claudication who had not responded to nonoperative treatment. (4) 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.  This study does not address the concerns noted above.

The FDA approval of the X STOP® Interspinous Process Decompression System was based on laboratory, mechanical and cadaver studies, and a multi-center, prospective randomized controlled clinical study. (5-7) In this clinical study, patients were randomized to either the XSTOP® at one (n=64) or two (n=36) levels or to a control group (n=91) which received continued non-operative therapy which included bed rest, a lumbar corset and a varied number of epidural injections. The Symptom Severity and Physical Function scores were measured at six weeks, six months, one year and two years. The scores for the X STOP® patients were significantly higher than the scores for the control group at each follow-up point.  At two years, the mean Symptom Severity score for the X-STOP® and the control groups was 45.4% above baseline scores and 7.4 (p<0.001), respectively.  The mean Physical Function score changes were 44.3% and -0.4% (p<0.001), respectively.  While these short-term results are promising, the study precludes scientific conclusions related to long-term health outcomes. A subsequent article was been published by the same authors using the 2-year quality of life date (SF-36) data from this trial. (8) As with other reports, 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. However, in this report the authors have considered the patients from both treatment and control groups who went on to have laminectomy within the 2-year follow-up period as lost to follow-up rather than as treatment failures. The article also notes a conflict of interest for the two primary authors of these articles.

Anderson and colleagues reported two year outcomes of a subset of patients in the original randomized trial reported above. (9) This subset consisted of patients in the randomized trial whose symptoms were due to degenerative spondylolisthesis at one or two levels.  The overall success was defined as a case in which all outcome measures (i.e., Zurich Claudication Questionnaire, Patient Satisfaction Survey, SF-36 scores, and additional surgery) were met.  In the X-STOP® group (n=42) 63.4% of patients met success criteria while 12.9% of the control group (n=33) met success criteria.  The difference was statistically significant.  Five patients (12%) in the X-STOP® group and four patients (12%) in the control group underwent laminotomy during the follow-up period.  Again, short-term results are encouraging but long-term outcomes are needed. In 2006, Kondrashov and Zucherman published the four year outcomes of another subset of patients in the randomized trial noted above. (10) Eighteen patients from one center were selected from the original nine-center sample based on the availability of preoperative Oswestry Disability Index (ODI) scores and willingness to complete the ODI at four years following surgery.  Using a 15 point improvement from baseline ODI score as a success criterion, 14 out of 18 patients (78%) had successful outcomes at the 4-year follow-up. The outcomes of the original control group were not included in this article.  This intermediate-term study suffered from the same design flaws noted previously, specifically, the small size, lack of a control group for comparison and lack of long-term health outcomes.

The addition of a DIAM™ Spinal Stabilization System implant to simple lumbar surgery (laminectomy and/or microdiscectomy) was examined in a case-control study of 62 patients. (11) 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 (n=31) in comparison with patients who had undergone laminectomy/microdiscectomy alone (n=31).

In March 2006 the National Institute for Clinical Excellence (NICE) in Great Britain conducted an evidence-based assessment of interspinous distraction devices/procedures for lumbar spinal stenosis causing neurogenic claudication. (12)  In their final guidance document the NICE reviewers stated that current evidence of efficacy is limited and is confined to short- and medium-term outcomes.  The reviewers noted concerns about additional pain in levels adjacent to the IPD device, device migration and potential infection. In a 2007 guideline, the North American Spine Society concluded that “there remains insufficient evidence to make a recommendation.” (13)

In summary, while studies report encouraging results when IPD is compared with a non-operative control group, the available evidence does not permit scientific conclusions concerning the effects of IPD on health outcomes. It remains unclear whether IPD improves the net health outcomes by providing sufficient relief to obviate the need for further surgery, or whether IPD is as effective as standard surgical decompression procedures in the long term. It also remains unclear whether the superior results in the X STOP® group of the randomized trial would deteriorate over time, as has been the case with other standard lumbar procedures.  The two and four year outcomes reported are intermediate only; longer term outcomes are needed in order to address these issues. A search of the MEDLINE database through October 10, 2008 failed to return any new published clinical trials which alter the above concerns related to the X STOP® device specifically and IPD in general. A prospective, Phase IV, five-year, post approval study of the X STOP® called the Condition of Approval Study (COAST) is currently in progress (NCT00517751). (14)

References

1. BlueCross and BlueShield Association, Medical Policy Reference Manual, Policy No. 7.01.107
2. 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):72-7
3. Siddiqui M, Nicol M, Karadimas E, et al.  The positional magnetic resonance imaging changes in the lumbar spine following insertion of a novel interspinous process distraction device. J Spinal Disord Tech 2005;30(23):2677-82
4. Siddiqui M, Karadimas E, Nicol M et al. Influence of X Stop on neural foramina and spinal canal area in spinal stenosis. Spine 2006;31(25):2958-62
5. www.fda.gov/cdrh/pdf4/P040001b.pdf (Verified 10/02/08)
6. Zucherman JF, Hsu KY, Hartjen CA et al. A prospective randomized multicenter study for the treatment of lumbar spinal stenosis with the X-STOP interspinous implant: 1-year results. Eur Spin J 2004;13(1):22-31
7. Zucherman JF, Hsu KY, Hartjen CA et al. A multicenter, prospective, randomized trial evaluating X-STOP interspinous process decompression system for the treatment of neurogenic intermittent claudication: two-year follow-up results. Spine 2005;30(12):1351-8
8. 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;5(6):500-7
9. 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;4:463-71
10. 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;19:323-327
11. Kim KA, McDonald M, Pik JH et al. Dynamic intraspinous spacer technology for posterior stabilization: case-control study on the safety, sagittal angulation, and pain outcome at 1-year follow-up evaluation. Neurosurg Focus 2007;22(1):E7.
12. Interspinous distraction procedures for lumbar spinal stenosis causing neurogenic claudication.  National Institute for Health and Clinical Excellence Interventional Procedure Guidance 165.  2006; online at www.nice.org.uk/page.aspx?o=ipg165guidance  (Verified 10/2/08)
13. North American Spine Society. Evidence-based clinical guidelines for multidisciplinary spine care: Diagnosis and treatment of degenerative lumbar spinal stenosis. January 2007 Available at:  http://www.spine.org/Documents/NASSCG_Stenosis.pdf  (Verified 10/2/08)
14. http://www.clinicaltrials.gov/ct/gui/show/NCT00517751?order=1 (Verified 10/2/08)

Cross References

Lumbar Dynamic Stabilization, Regence Medical Policy Manual, Surgery, Policy No. 143

Lumbar Spine Surgery, Regence Medical Policy Manual, Surgery, Policy No. 101

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