Interspinous Fixation (Fusion) Devices
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Interspinous fixation (fusion) devices are being developed to aid in the stabilization of the spine. They are being evaluated as alternatives to pedicle screw and rod constructs in combination with interbody fusion. Interspinous fixation devices are also being evaluated for stand-alone use in patients with spinal stenosis.
Contemporary models of interspinous fixation devices have evolved from spinous process wiring with bone blocks and early device designs (e.g., Wilson plate, Meurig-Williams system, Daab plate). The newer devices range from paired plates with teeth to U-shaped devices with wings that are attached to the spinous process. They are intended to be an alternative to pedicle screw and rod constructs to aid in the stabilization of the spine with interbody fusion. Interspinous fixation devices are placed under direct visualization, while screw and rod systems may be placed either under direct visualization or percutaneously. Use of an interspinous fixation device in combination with a unilateral pedicle screw system has also been proposed. Interspinous fixation devices are not intended for stand-alone use.
Interspinous fixation (fusion) devices contrast with interspinous distraction devices (spacers), which are used alone for decompression and are typically not fixed to the spinous process. In addition, whereas interspinous distraction devices may use dynamic stabilization, interspinous fixation devices are rigid. However, the fixation devices might also be used to distract the spinous processes and decrease lordosis. Thus, the fixation devices might be used without interbody fusion as decompression (distraction) devices in patients with spinal stenosis. If fixation devices are used alone as a spacer, there is a risk of spinous process fracture.
For use in combination with fusion, it is proposed that interspinous fixation systems are less invasive and present fewer risks than pedicle or facet screws. However, while biomechanical studies indicate that interspinous fixation devices may be similar to pedicle screw-rod constructs in limiting the range of flexion-extension, they may be less effective than bilateral pedicle screw-rod fixation for limiting axial rotation and lateral bending. There is a potential for a negative impact on the interbody cage and bone graft due to focal kyphosis resulting from the interspinous device. There is also a potential for spinous process fracture.
The following interspinous fixation devices have received clearance to market by the U.S. Food and Drug Administration (FDA). This may not be an exhaustive list.
- Affix™ (NuVasive)
- Aileron™ (Life Spine)
- Aspen™ (Lanx)
- Axle™ (X-Spine)
- BacFuse® (Pioneer Surgical)
- BridgePoint™ (Alphatec)
- coflex-F® (Paradigm Spine)
- Inspan™ (Spine Frontier)
- PrimaLOK™ (OsteoMed)
- Octave™ (Life Spine)
- Spire™ (Medtronic)
- SP-Fix™ (Globus)
Interspinous fixation devices are intended to be used as an adjunct to interbody fusion. For example, the indication for use of the coflex-F implant “is a posterior, non-pedicle supplemental fixation device intended for use with an interbody cage as an adjunct to fusion at a single level in the lumbar spine (L1-S1). It is intended for attachment to the spinous processes for the purpose of achieving stabilization to promote fusion in patients with degenerative disc disease – defined as back pain of discogenic origin with degeneration of the disc confirmed by history and radiographic studies – with up to Grade 1 spondylolisthesis.” Use of an interspinous fixation device for a stand-alone procedure would be considered off-label.
- Interspinous Distraction Procedure for Lumbar Spinal Stenosis (Policy #065 in the Surgery Section of this database)
- Lumbar Spinal Fusion (Policy #073 in the Surgery Section of this database)
1. Interspinous fixation (fusion) device when used as an adjunct to interbody fusion is subject to the medical necessity of the primary lumbar spinal fusion procedure.
[NOTE: Please refer to a separate policy on 'Lumbar Spinal Fusion' (Policy #073) under the Surgery Section of this database.]
2. Interspinous fixation (fusion) device is considered investigational for all other uses including, but not limited to, as stand-alone use in members with spinal stenosis.
Use of the Aspen interspinous fixation device as a stand-alone interspinous spacer was reported in a prospective series of 6 cases (an additional 32 patients received the X-stop interspinous distraction device). The study population consisted of consecutive patients with a primary diagnosis of lumbar spinal stenosis with pain that was relieved by sitting or lumbar flexion. Of the 6 patients implanted with the Aspen device, 2 (33%) had spinous process fractures observable on computed tomography (CT). Out of the entire group of 38 patients, 55% of those with spondylolisthesis (n=20) had a fracture within 6 months of surgery. None of the 18 patients without spondylolisthesis experienced a fracture.
Clinical Input Received through Physician Specialty Societies and Academic Medical Centers
While the various physician specialty societies and academic medical centers may collaborate with and make recommendations during this process through the provision of appropriate reviewers, input received does not represent an endorsement or position statement by the physician specialty societies or academic medical centers, unless otherwise noted.
In response to requests, input was received from 3 physician specialty societies (2 reviewers) and 2 academic medical centers in 2012. The input was mixed. Some cases where the devices might be medically necessary were noted, such as patients with small pedicles where pedicle screws could not be safely placed.
There is a lack of evidence on the efficacy of interspinous fixation devices for use as a stand-alone procedure. Clinical trials are needed to evaluate these devices when used alone for decompression.
Medicare National Coverage
No national coverage decisions were identified.]
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This Horizon BCBSNJ Medical Policy (the “Medical Policy”) has been developed by Horizon BCBSNJ’s Medical Policy Committee (the “Committee”) consistent with generally accepted standards of medical practice, and reflects Horizon BCBSNJ’s view of the subject health care services, supplies or procedures, and in what circumstances they are deemed to be medically necessary or experimental/ investigational in nature. This Medical Policy also considers whether and to what degree the subject health care services, supplies or procedures are clinically appropriate, in terms of type, frequency, extent, site and duration and if they are considered effective for the illnesses, injuries or diseases discussed. Where relevant, this Medical Policy considers whether the subject health care services, supplies or procedures are being requested primarily for the convenience of the covered person or the health care provider. It may also consider whether the services, supplies or procedures are more costly than an alternative service or sequence of services, supplies or procedures that are at least as likely to produce equivalent therapeutic or diagnostic results as to the diagnosis or treatment of the relevant illness, injury or disease. In reaching its conclusion regarding what it considers to be the generally accepted standards of medical practice, the Committee reviews and considers the following: all credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community, physician and health care provider specialty society recommendations, the views of physicians and health care providers practicing in relevant clinical areas (including, but not limited to, the prevailing opinion within the appropriate specialty) and any other relevant factor as determined by applicable State and Federal laws and regulations.
Interspinous Fixation (Fusion) Devices
1. Wu JC, Mummaneni PV. Using lumbar interspinous anchor with transforaminal lumbar interbody fixation. World Neurosurg 2010; 73(5):471-2.
2. Kim DH, Shanti N, Tantorski ME et al. Association between degenerative spondylolisthesis and spinous process fracture after interspinous process spacer surgery. Spine J 2012; 12(6):466-72.
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