Surgery Section - Lumbar Dynamic Stabilization

IMPORTANT REMINDER

Regence Medical Policies are developed to provide guidance for members and providers regarding coverage in accordance with contract terms. Benefit determinations are based in all cases on the applicable contract language. To the extent there may be any conflict between the Medical Policy and contract language, the contract language takes precedence.

PLEASE NOTE: Contracts exclude from coverage, among other things, services or procedures that are considered investigational or cosmetic. Providers may bill members for services or procedures that are considered investigational or cosmetic. Providers are encouraged to inform members before rendering such services that the members are likely to be financially responsible for the cost of these services.

DESCRIPTION

Degenerative changes of the spinal column are the most common underlying cause of chronic low back pain (LBP). As individuals age, degenerative changes accumulate, affecting the vertebral discs, vertebra, facet joints, and ligaments in the lumbar region and can lead to compression of spinal nerves and spinal nerve roots.

When conservative treatment fails to control the pain of degenerative disc disease, stenosis and spondylolisthesis, a common surgical approach is spinal fusion. However, the outcomes of spinal fusion have been controversial over the years, in part due to the difficulty in determining whether a patient’s back pain is related to degenerative disc disease. 

Dynamic stabilization, also known as soft stabilization or flexible stabilization, has been proposed as an adjunct or alternative to fusion.  Dynamic stabilization uses flexible materials to stabilize the affected lumbar region while preserving the natural anatomy of the spine.  It is intended to alter the load bearing pattern of the motion segment and to control any abnormal motion while leaving the spinal segment mobile.  This is differentiated from semirigid fixation of the spine for which a fusion is intended.  The hypothesis behind stabilization is that control of abnormal motions and more physiologic load transmission would relieve pain and prevent adjacent segment degeneration.  The expectation is that once normal motion and load transmission are achieved, the damaged disc may repair itself, unless the degeneration is too advanced.

Regulatory Status

The following dynamic stabilization devices have received clearance from the U.S. Food and Drug Administration (FDA):

• Dynesys® System (Zimmer, Inc)
  
  
• CD HORIZON® AGILE™ Dynamic Stabilization device (Medtronic Sofamor Danek, Inc.)
  
  
• NFix™ II Dynamic Stabilization System (N Spine, Inc.)
  
  
• Satellite™ Spinal System (Medtronic Sofamor Danek, Inc.)
  
  
• BioFlex System with Nitinol spring rod and memory loops (Bio-Spine)
  
  
• DSS (Dynamic Soft Stabilization) system (Paradigm Spine)
  

The FDA clearance for these devices is limited to use as an adjunct to spinal fusion of the thoracic, lumbar and sacral spine for degenerative spondylolisthesis with neurologic impairment, and for failed previous fusion (pseudoarthrosis).  When used as a pedicle screw fixation system, these devices are indicated for use in patients who are receiving fusion of the lumbar or sacral spine with autogenous graft only, and who are having the device removed after development of a solid fusion mass. Clinical trials are ongoing for use of the Dynesys® and the NFlex™ systems in the absence of fusion but no dynamic stabilization devices have received FDA approval for this indication.

The following dynamic stabilization devices have been investigated but have not received FDA clearance:

• Bronsard’s Ligament
  
  
• FASS (Fulcrum Assisted Soft Stabilization)
  
  
• Graf ligament
  
  
• Leeds-Keio Ligamentoplasty
  
  
• Loop system
  
  
• NFlex™ Controlled Motion System (indicated for non-fusion only) (N Spine, Inc.)
  
  
• Stabilimax NZ® Dynamic Spine Stabilization System (Applied Spine Technologies Inc.)

Note: This policy considers only dynamic stabilization devices across pedicle screws. Interspinous spacers are considered separately in policy Surgery No.155, Interspinous Process Decompression.

POLICY/CRITERIA

Lumbar dynamic stabilization using any device is considered investigational for the treatment of disorders of the lumbar and sacral spine.

SCIENTIFIC BACKGROUND

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. In addition, because of constant movement of the stabilized segment, it is important to determine the failure rate of dynamic stabilization over the long-term and compare these outcomes with the outcomes following fusion.

In a 2004 review article, Sengupta identified the pertinent questions in dynamic stabilization as: (a) how much control of motion is desirable, and (b) how much load should be shared by the system to unload the damaged disc. ^[1] The author concluded that, while dynamic stabilization procedures may prove to have a promising role in preventing the adjacent segment disease inherent with fusion, randomized controlled trials are essential to prove safety, efficacy and appropriateness of these procedures.  Schwarzenbach and colleagues reached the same conclusion in their recent review article. ^[2]

Literature Review

To date, only one randomized clinical trial has been reported. The bulk of published literature currently available consists of review articles and poorly designed studies which preclude scientific analysis.  Some of the methodological flaws in these studies include non-randomization and selection bias, investigator conflict of interest, under-reporting of adverse events which could have been related to the device, lack of a control group and notable differences in outcomes between study centers.

Randomized, controlled trials

Korovessis and colleagues reported on a study of 45 adults randomized into three groups. ^[3] All patients had decompression and fusion with instrumentation as follows:  Group A had rigid instrumentation, Group B had semi-rigid instrumentation, and Group C had dynamic instrumentation.  Follow-up was between 33 and 61 months.  All fusions in all three groups healed without pseudoarthrosis or malunion within six months after surgery.  Hardware failures were seen only in the dynamic instrumentation group and included one asymptomatic and one symptomatic pedicle screw breakage and one symptomatic rod breakage.  Donor site pain for six to twelve months postoperatively was reported only in the rigid and semirigid instrumentation groups.  There was no degeneration at the adjacent vertebral segments above or below the instrumentation level in any group.  Due to the small number of patients and the need for longer follow-up, the authors make no recommendation in favor of any of the devices used in this study.

Nonrandomized trials

There are a number of small case series trials ^[4-10] and retrospective reviews ^[11-13] which are unreliable for the reasons noted above.  In addition, these studies are small, including less than 100 subjects; small study populations limit the ability to rule out the role of chance as an explanation of study findings. All but one included only short-term follow-up data. The study with the longest duration was 4 years, which is considered intermediate-term data for spinal surgeries. ^[10] However, the data from this study are unreliable because the outcomes are based on only 19 of the original 26 patients, a 27% loss to follow-up.  

Clinical Practice Guidelines and Position Statements

No practice guidelines or position statements from U.S. professional associations were found that recommend use of lumbar dynamic stabilization.

Summary

The absence of well-developed randomized clinical trials with long-term follow-up does not allow conclusions concerning the safety and efficacy of dynamic stabilization in the treatment of degenerative disc disease.

REFERENCES

1. Sengupta, DK. Dynamic stabilization devices in the treatment of low back pain. Orthop Clin North Am. 2004 Jan;35(1):43-56.  PMID: 15062717
2. Schwarzenbach, O, Berlemann, U, Stoll, TM, Dubois, G. Posterior dynamic stabilization systems: DYNESYS. Orthop Clin North Am. 2005 Jul;36(3):363-72.  PMID: 15950696
3. Korovessis, P, Papazisis, Z, Koureas, G, Lambiris, E. Rigid, semirigid versus dynamic instrumentation for degenerative lumbar spinal stenosis: a correlative radiological and clinical analysis of short-term results. Spine (Phila Pa 1976). 2004 Apr 1;29(7):735-42.  PMID: 15087795
4. Kim, KA, McDonald, M, Pik, JH, Khoueir, P, Wang, MY. 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.  PMID: 17608341
5. Kim, YS, Zhang, HY, Moon, BJ, et al. Nitinol spring rod dynamic stabilization system and Nitinol memory loops in surgical treatment for lumbar disc disorders: short-term follow up. Neurosurg Focus. 2007;22(1):E10.  PMID: 17608331
6. Welch, WC, Cheng, BC, Awad, TE, et al. Clinical outcomes of the Dynesys dynamic neutralization system: 1-year preliminary results. Neurosurg Focus. 2007;22(1):E8.  PMID: 17608342
7. Kaner, T, Sasani, M, Oktenoglu, T, Cosar, M, Ozer, AF. Utilizing dynamic rods with dynamic screws in the surgical treatment of chronic instability: a prospective clinical study. Turk Neurosurg. 2009 Oct;19(4):319-26.  PMID: 19847749
8. Kaner, T, Dalbayrak, S, Oktenoglu, T, Sasani, M, Aydin, AL, Ozer, AF. Comparison of posterior dynamic and posterior rigid transpedicular stabilization with fusion to treat degenerative spondylolisthesis. Orthopedics. 2010 May;33(5).  PMID: 20506953
9. Richter, A, Schutz, C, Hauck, M, Halm, H. Does an interspinous device (Coflex) improve the outcome of decompressive surgery in lumbar spinal stenosis? One-year follow up of a prospective case control study of 60 patients. Eur Spine J. 2010 Feb;19(2):283-9.  PMID: 19967546
10. Schaeren, S, Broger, I, Jeanneret, B. Minimum four-year follow-up of spinal stenosis with degenerative spondylolisthesis treated with decompression and dynamic stabilization. Spine (Phila Pa 1976). 2008 Aug 15;33(18):E636-42.  PMID: 18708915
11. 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 (Phila Pa 1976). 2005 Feb 1;30(3):324-31.  PMID: 15682014
12. Sapkas, GS, Themistocleous, GS, Mavrogenis, AF, Benetos, IS, Metaxas, N, Papagelopoulos, PJ. Stabilization of the lumbar spine using the dynamic neutralization system. Orthopedics. 2007 Oct;30(10):859-65.  PMID: 17990413
13. Taylor, J, Pupin, P, Delajoux, S, Palmer, S. Device for intervertebral assisted motion: technique and initial results. Neurosurg Focus. 2007;22(1):E6.  PMID: 17608340

CROSS REFERENCES

Interspinous Distraction Devices (Spacers), Regence Medical Policy Manual, Surgery, Policy No. 155

Total Facet Arthroplasty, Regence Medical Policy Manual, Surgery, Policy No. 171

Spinous Process Fixation Orthosis, Regence Medical Policy Manual, Surgery, Policy No. 172

Image-Guided Minimally Invasive Lumbar Decopression (IG-MLD) for Spinal Stenosis, Regence Medical Policy Manual, Surgery, Policy No. 176

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