Surgery Section - Lumbar Dynamic Stabilization

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

Degenerative changes of the spinal column are the most common underlying cause of chronic low back pain (LBP). The peak incidence of symptoms occurs between the ages of 30 and 50, probably because this is the period of life during which the most strenuous job and sports-related activities occur. 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; over 200,000 spinal fusions are performed each year. The disc and other material that may be compressing nerve roots is removed and the vertebrae superior and inferior to the removed disc are fused. 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. In addition, spinal fusion alters the biomechanics of the back, potentially leading to premature disc degeneration at adjacent levels, a particular concern for younger patients.

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.

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.)

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:

• BioFlex System with Nitinol spring rod and memory loops (Bio-Spine)
  
• Bronsard’s Ligament
  
• DSS (Dynamic Soft Stabilization) system
  
• FASS (Fulcrum Assisted Soft Stabilization)
  
• Graf ligament
  
• Leeds-Keio Ligamentoplasty
  
• Loop system
  
• NFlex™ Controlled Motion System (indicated for non-fusion only)
  
• Stabilmax 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

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. The 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.

Korovessis and colleagues reported on a study of 45 adults randomized into three groups. (1) 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.

Gorb and colleagues reported on a retrospective study in which 50 consecutive patients instrumented with Dynesys® within 24 to 40 months prior to this study were asked to respond to a questionnaire. (2) Only thirty-one (64%) of the 50 subjects completed the questionnaire. The results indicated that both back and leg pain were, on average, still moderately high two years after instrumentation with the Dynesys® system. Half of the subjects reported that instrumentation had improved quality of life; less than half reported improvements in functional capacity. The reoperation rate was relatively high at 19%. The authors concluded that these results provide no support for the notion that semirigid fixation of the lumbar spine results in better patient-oriented outcomes than those typical of 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. (3) 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 reach the same conclusion in their recent review article. (4)

In June 2006 the European National Institute for Health and Clinical Excellence (NICE) in Great Britain conducted an evidence-based assessment of non-rigid stabilization procedures for the treatment of low back pain with the following conclusion:

“Limited evidence suggests that non-rigid stabilisation procedures for the treatment of low back pain provide clinical benefit for a proportion of patients with intractable back pain. Current evidence on the safety of these procedures is unclear and involves a variety of different devices and outcome measures. Therefore, these procedures should only be used with special arrangements for consent and for audit or research.” (5)

A search of the MEDLINE database through October 10, 2008 continue to return nonrandomized, short-term case series and retrospective reviews. (6-10)  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. Korovessis P, Papazisis Z, Doureas G, et al. Rigid, semirigid versus dynamic instrumentation for lumbar spinal stenosis. Spine 2004;29(7):735-42
2. Grob D, Benini A, Junge A, et al. 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):324-31
3. Sengupta DK. Dynamic stabilization devices in the treatment of low back pain. Orthop Clin North Am 2004;35(1):43-56
4. Schwarzenbach O, Berleman U, Stoll TM et al. Posterior dynamic stabilization systems: DYNESYS. Orthop Clin North Am 2005;36(3):363-72
5. Non-rigid stabilisation techniques for the treatment of low back pain - guidance National Institute for Health and Clinical Excellence Interventional Procedure Guidance 183. 2006; online at http://guidance.nice.org.uk/IPG183/guidance/pdf/English (Verified 10/2/08)
6. Taylor J, Pupin P, Delajoux S, ET AL. Device for intervertebral assisted motion: technique and initial results.Neurosurg Focus 2007;22(1):E6
7. 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
   
8. 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
   
9. 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
10. Sapkas GS, Themistocleous GS, Mavrogenis AF, et al. Stabilization of the lumbar spine using the dynamic neutralization system. Orthopedics. 2007;30(10):859-65

Cross References

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

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

Surgery Section Table of Contents