Interspinous Fixation (Fusion) Devices
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 (see policy Related Policies). 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 off-label 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. (1) 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. Given these uncertainties, studies are needed that compare health outcomes between interspinous fixation devices and pedicle screw-rod fixation.
The following interspinous fixation devices have received clearance to market by FDA. This may not be an exhaustive list.
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.
FDA Product code: PEK.
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Several studies were identified that evaluated the biomechanics of interspinous fixation devices, but no English language publications were found that evaluated clinical outcomes with use of these devices when used in combination with fusion.
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, which is addressed in Related Policies). (2) 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. 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. In 2013, use of an interspinous fusion plate was reported in a series of 4 patients in conjunction with surgery for recurrent lumbar disc herniation.3
Ongoing and Unpublished Clinical Trials
A search of online site ClinicalTrials.gov in July 2014 found the following ongoing trials:
Clinical Input Received from 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 while this policy was under review 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.
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. There is a lack of evidence on the efficacy of interspinous fixation devices, both for use in combination with interbody fusion and for use as a stand-alone procedure. Randomized controlled trials are needed that evaluate health outcomes following use of interspinous fixation (fusion) devices in comparison with the established standard of pedicle screw-rod fixation. Clinical trials are also needed to evaluate these devices when used alone for decompression. Because of the lack of evidence and the lack of consensus from clinical vetting, interspinous fixation devices are considered investigational.
Practice Guidelines and Position Statements
The North American Spine Society (NASS) issued a coverage position on the use of interspinous devices with lumbar fusion.4 NASS recommends that interspinous fixation with fusion for stabilization is currently not indicated as an alternative to pedicle screw fixation with lumbar fusion procedures.
U.S. Preventive Services Task Force Recommendations
Use of interspinous fixation devices is not a preventive service.
Medicare National Coverage
There is no national coverage determination (NCD). In the absence of an NCD, coverage decisions are left to the discretion of local Medicare carriers.
Posterior non-segmental instrumentation (e.g., Harrington rod technique, pedicle fixation across 1 interspace, atlantoaxial transarticular screw fixation, sublaminar wiring at C1, facet screw fixation)
Application of intervertebral biomechanical device(s) (e.g., synthetic cage(s), methylmethacrylate) to vertebral defect or interspace
New policy. Policy created with literature search through July 2012; considered investigational.
Update Related Policies, add 7.01.130.
Replace policy. Policy updated with literature review through July 30, 2013; policy statement unchanged.
Disclaimer: This medical policy is a guide in evaluating the medical necessity of a particular service or treatment. The Company adopts policies after careful review of published peer-reviewed scientific literature, national guidelines and local standards of practice. Since medical technology is constantly changing, the Company reserves the right to review and update policies as appropriate. Member contracts differ in their benefits. Always consult the member benefit booklet or contact a member service representative to determine coverage for a specific medical service or supply. CPT codes, descriptions and materials are copyrighted by the American Medical Association (AMA).