Rigid spinal fixation instrumentation generally includes pedicle screws with rods and anterior or posterior interbody cages. Non-pedicle fixation devices have been developed and have U.S. Food and Drug Administration (FDA) 510(k) clearance. These devices are affixed to the spinous process to achieve fixation. They also accommodate bone graft material for fusion and are not intended to be used for stand-alone use per the FDA 510(k) clearance.

These interspinous fixation devices differ from interspinous process spacers (e.g., X STOP^®_, Medtronic Inc., Minneapolis, MN) and dynamic stabilization systems (e.g., Dynesys^®_, Zimmer Inc., Minneapolis, MN) that are motion preserving devices.

Note: Please see the following related documents for additional information:

• SURG.00075 Intervertebral Stabilization Devices
• SURG.00092 Implanted Devices for Spinal Stenosis

Investigational and Not Medically Necessary:

Interspinous fixation devices are considered investigational and not medically necessary for all indications.

The standard surgical procedure for rigid spinal fixation involves the use of pedicle screws, rods and plates. However, the pedicle may not support fixation due to osteoporosis, trauma, or previous pedicle fixation failure.

Non-pedicle spinal fixation devices were developed as an alternative. Examples of these devices include, but are not limited to: Aspen™ Spinous Process Fixation System (Lanx Inc., Broomfield, Colorado); CD HORIZON^® SPIRE Plate (Medtronic Inc., Memphis, TN); SP-Fix™ Spinous Process Fixation Plate (Globus Medical Inc., Audubon, PA) and PrimaLOK™SP (OsteoMed, Addison, TX).

The FDA 510(k) clearance does not require clinical trials, but requires a predicate device for the applicant device prior to marketing. The interspinous fixation devices (with or without additional instrumentation) are marketed as a minimally invasive rigid fixation alternative to standard rigid fixation instrumentation using pedicle screws and rods or interbody cages. However, there are no studies comparing interspinous fixation devices to standard pedicle fixation. The current published evidence consists of 2 articles for the Aspen device describing the biomechanical effect of  the Aspen device on cadaver spines (Kaibara, 2012; Karahalios, 2010).

A randomized, single blinded (participant) industry-sponsored clinical trial, A Multi-Center Prospective Randomized Study Comparing Supplemental Posterior Instrumentation, Aspen™ Spinous Process System Versus Pedicle Screw Fixation, in Lateral Lumbar Interbody Fusion (LLIF) or Anterior Lumbar Interbody Fusion (ALIF), is currently recruiting participants. Study completion is anticipated in March 2014.

The interspinous devices have similar indications:

1. Degenerative disc disease (DDD)
2. Spondylolisthesis
3. Trauma (i.e. fracture or dislocation)
4. Tumor
5. Pseudarthrosis
6. Failed previous fusion

Some devices can be used as an adjunct to surgery:

1. Supplemental fixation for ALIF procedures
2. Supplemental fixation for TLIF procedures
3. Supplemental fixation lateral interbody fusion procedures
4. Posterior interlaminar fusion
5. Posterolateral fusion
6. Revision option in failed fusion/hybrid constructs

Vertebral Anatomy and Interspinous Fixation Devices

The pedicle is a small area of bone that is the first to extend out from both sides of the back of the vertebral body and joins with broad flat plates of bone (laminae) to form a hollow archway that protects the spinal cord. One type of fixation involves pedicle screws that are inserted as anchors for rods that provide fixation. Another type of fixation is the interbody cage. This is a titanium cylinder that is placed in the disc space. Both of these techniques support fusion when bone graft material is used.

The interspinous fixation device is attached to a vertebral spinous process. Interspinous fixation devices are designed for use as an adjunct to instrumented vertebral fixation providing additional fixation as well as a compartment for bone graft material for fusion.

Lamina: Part of the vertebra located behind the vertebral body. A flat area of bone between the superior process forming the facet joint and the spinous process, helping to form the central canal through which the spinal cord passes.

Pedicles: Two short, rounded processes made of thick cortical bone that extend posteriorly from the lateral margin of the dorsal surface of the vertebral body.

Spinous Process: The small, bony protuberances located along the back of the spinal column that act as attachment sites for muscles and ligaments.

Spinal fusion: A surgical procedure to stabilize the spine by fusing together two or more vertebrae.

Spondylolisthesis: A condition that occurs when one vertebra slips out of the proper position onto the bone below it.

The following codes for treatments and procedures applicable to this document are included below for informational purposes. A draft of future ICD-10 Coding (effective 10/01/2014) related to this document, as it might look today, is included below for your reference.  Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy  Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

When services are Investigational and Not Medically Necessary:
When the code describes a procedure indicated in the Position Statement section as investigational and not medically necessary.

Peer Reviewed Publications:

1. Kaibara T, Karahalios DG, Porter RW, et al. Biomechanics of a lumbar interspinous anchor with transforaminal lumbar interbody fixation. World Neurosurg. 2010; 73(5):572-577.
2. Karahalios DG, Kaibara T, Porter RW, et al. Biomechanics of a lumbar interspinous anchor with anterior lumbar interbody fusion. J Neurosurg Spine. 2010; 12(4):372-380.

Government Agency, Medical Society, and Other Authoritative Publications: 

1. Lanx, Inc. A multi-center prospective randomized study comparing supplemental posterior instrumentation, Aspen™ Spinous Process System versus pedicle screw fixation, in lateral lumbar interbody fusion (LLIF) or anterior lumbar interbody fusion (ALIF). NLM Identifier: NCT01549366. Last updated on May 11, 2012. Available at: http://clinicaltrials.gov/ct2/show/NCT01549366. Accessed on June 15, 2012.
2. U.S. Food and Drug Administration 510(k) Premarket Notification Database. Aspen™ Spinous Process Fixation System. Summary of Safety and Effectiveness. No. K071877. Rockville, MD: FDA. September 17, 2007. Available at:http://www.accessdata.fda.gov/scripts/cdrh/devicesatfda/index.cfm?db=pmn&id=K071877. Accessed on June 15, 2012.
3. U.S. Food and Drug Administration 510(k) Premarket Notification Database. PrimaLOK™ SP. Summary of Safety and Effectiveness. No. K100354. Rockville, MD: FDA. August 17, 2010. Available at: http://www.accessdata.fda.gov/scripts/cdrh/devicesatfda/index.cfm?db=pmn&id=K100354. Accessed on June 15, 2012.

1. U.S. National Library of Medicine. Medline Plus. Spinal fusion. Available at: http://vsearch.nlm.nih.gov/vivisimo/cgi-bin/query-meta?v%3Aproject=medlineplus&query=spinal+fusion&x=21&y=18. Accessed on June 15, 2012.

Aileron^® Interspinous Fixation System
Aspen™ Spinous Process Fixation System
CD HORIZON^® SPIRE Plate
Coflex-F^® Implant
Interspinous Fixation Devices
PrimaLOK^TMSP
SP-Fix^TM Spinous Process Fixation Plate

The use of specific product names is illustrative only.  It is not intended to be a recommendation of one product over another, and is not intended to represent a complete listing of all products available.