Medical Policy


Subject: Interspinous Process Fixation Devices
Document #: SURG.00134 Publish Date:    08/29/2018
Status: Reviewed Last Review Date:    07/26/2018


This document addresses interspinous, non-pedicle fixation devices attached to the spinous process to achieve rigid spinal fixation and accommodate bone graft material for spinal fusion.

Note: Interspinous process fixation devices in this document differ from interspinous process spacers and dynamic stabilization systems that are motion preserving devices. Please see the following related documents for additional information concerning these devices:

Position Statement

Investigational and Not Medically Necessary:

Interspinous process 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. Non-pedicle interspinous process fixation devices (with or without additional instrumentation) were developed as a minimally invasive rigid fixation alternative to standard rigid fixation instrumentation using pedicle screws and rods or interbody cages. According to the U.S. Food and Drug Administration (FDA) 510(k) clearance, interspinous process fixation devices are intended for use with bone graft material and are not intended for stand-alone use.

The available evidence in the peer-reviewed published medical literature comparing the Aspen® Spinous Process Fixation System (Lanx Inc./Biomet Spine, Inc, Broomfield, Colorado) to standard pedicle fixation includes two articles describing the biomechanical effect of the device on cadaver spines (Kaibara, 2012; Karahalios, 2010) and a small prospective study evaluating individuals with a primary diagnosis of lumbar spinal stenosis (with pain) treated with the Aspen device or an interspinous process spacer (Kim, 2012a). Of the 6 individuals implanted with the Aspen device (as a stand-alone procedure), 2 (33%) had postoperative spinous process fractures observable on computed tomography (CT). Limitations of this study include the small sample size, heterogeneous population, and lack of outcome measures reporting a change in Oswestry Disability Index (ODI) or a reduction in pain medication usage.

Kim and colleagues (2012b) retrospectively compared 40 individuals who underwent single level spinal fusion with the CD HORIZON® SPIRE™ (Medtronic Sofamor Danek, Inc., U.S.A., Memphis, TN) interspinous fusion device (IFD) for lumbar spine disease (n=12, degenerative spondylolisthesis; n=2, intervertebral disc herniation; n=26, spinal stenosis) to 36 individuals with similar lumbar spinal disorders (n=10, degenerative spondylolisthesis; n=7, foraminal stenosis; n=1, intervertebral disc herniation; n=18, spinal stenosis) who underwent spinal fusion with pedicle screw fixation. All individuals in both groups underwent posterior lumbar interbody fusion with a polyetheretherketone cage or a titanium alloy cage. Both groups were evaluated using dynamic lateral radiographs, visual analogue scale (VAS), and a Korean version of the Oswestry Disability Index (K-ODI) scores. The mean follow-up period was 14.24 months in the IFD group and 18.3 months in pedicle screw group. At 1-year follow-up, there was an improvement in the mean preoperative to postoperative VAS scores from 7.16 (± 2.1) to 1.3 (± 2.9) and 8.03 (± 2.3) to 1.2 (± 3.2) (p<0.05) in the IFD and pedicle screw groups, respectively. The K-ODI was reduced significantly in an equal amount in both groups 1 year postoperatively (p<0.05); however, no statistical difference in clinical outcomes was noticed between the 2 groups. Postoperative radiographs in the IFD group showed less improvement of instability at the instrumented level compared with the pedicle screw group. A higher incidence of adjacent segmental degeneration was reported in the pedicle screw group (n=13, 36.1%) than in the IFD group (n=5, 12.5%; p=0.029). In the IFD group, 1 individual had sustained back pain, and lumbar CT revealed fusion failure and inferior articular process fracture. There were no major surgery-related complications such as deep infection, nerve root injury, and cerebral spinal fluid (CSF) leakage in the IFD group; however, in the pedicle screw group, 3 individuals developed deep infection, 2 individuals experienced CSF leakage, and 1 individual required re-operation for a postoperative epidural hematoma. Limitations of this study include the retrospective, nonrandomized design, the heterogeneous population of participants in terms of preoperative diagnoses, and a relatively short-term follow-up period.

Scalfani and colleagues (2014) retrospectively reviewed medical records to evaluate postoperative clinical outcomes in 53 individuals who were implanted with a second generation polyaxial PrimaLOK™ SP Interspinous Fusion System (OsteoMed, Addison, TX). All subjects reached the 1-year postoperative time point. Subjects had a mean age of 60 years (range, 34-89 years) at the time of surgery. The most common primary surgical indications were degenerative disc disease with stenosis (45.3%), herniated disc (18.9%) and spondylolisthesis (11.3%). A total of 34 subjects were implanted with the PrimaLOK SP device, 16 subjects received both a polyetheretherketone interbody cage and the PrimaLOK SP device, and 3 subjects received pedicle screw instrumentation, a polyetheretherketone interbody cage and the PrimaLOK SP device. Complications included intraoperative dural tear (n=1) and readmission for intractable pain after a post-discharge mechanical fall (n=1). There were no cases of fracture or migration of the device observed at the 6-week postoperative time point; however, there were 4 cases of hardware removal and 2 cases of re-operation for adjacent level disease during the follow-up period. The pain index score improved from 7.17 ± 1.68 to 4.48 ± 2.8 (p=0.0001, 22 months average follow-up) for the overall study group. There was no difference in Macnab classification score between different primary surgical indication groups (χ2 p>0.05). Limitations of this review include the retrospective study design and lack of data collection on preoperative VAS scores of low back and leg pain and validated quality of life of life data to distinguish if the postoperative improvement was predominantly in axial low back pain, radicular lower extremity pain or neurogenic claudication.

Lopez and colleagues (2017) systematically evaluated the literature on lumbar spinous process fixation and fusion devices (excluding dynamic fixation and spinous process spacer devices). A total of 15 articles met the inclusion and exclusion criteria, including 4 comparative studies (level III evidence), 2 case series (level IV evidence), and 9 in vitro biomechanics studies (level V evidence). Two of the nonrandomized studies compared interspinous process fixation devices to pedicle screws in individuals undergoing interbody fusion and two other studies included interspinous process fixation devices alone or pedicle screws plus an interspinous process fixation device in individuals undergoing interbody fusion. Use of an interspinous process fixation device decreased surgical time and blood loss compared to pedicle screw implantation procedures, however, study designs were methodologically flawed and biased when reporting outcomes of reduced spinal instability at 1 year, rates of device failure, bony fracture, and complications. No comparative studies exist that report either complication rates of interspinous process fixation devices to other treatment modalities or length of hospital stay for interspinous process fixation devices compared to pedicle screw implantation procedures.

In summary, there is a lack of evidence in the peer-reviewed published medical literature to support the long-term safety and effectiveness of interspinous process fixation devices when used in combination with interbody fusion or as a stand-alone procedure. Randomized controlled trials are needed to demonstrate the clinical utility of interspinous process fixation devices compared with established standard surgical approaches involving pedicle screw-rod fixation with lumbar fusion procedures.

Other Considerations

In 2014, the North American Spine Society (NASS) issued coverage policy recommendations for the clinical indications for interspinous process fixation devices marketed as an alternative to pedicle screw fixation for lumbar fusion, stating:

Interspinous fixation with fusion for stabilization is currently NOT indicated as an alternative to pedicle screw fixation with lumbar fusion procedures…To our knowledge, there are no prospective, randomized, controlled trials evaluating the efficacy or safety of this class of devices compared to the gold standard (pedicle screws) with sufficient follow-up.

NASS is currently in the process of reviewing their 2014 recommendations and is expected to issue an updated coverage policy in 2018.


Vertebral Anatomy and Interspinous Process 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 placed in the disc space. Both of these fixation devices support fusion when used with bone graft material.

Interspinous process fixation devices attach to a vertebral spinous process and are intended for use as an adjunct to instrumented vertebral fixation procedures as well as a compartment for bone graft material for fusion. Interspinous process fixation devices have been proposed for use after failed spinal fusion procedures and for treatment of degenerative disc disease, pseudoarthrosis, spondylolisthesis, trauma (dislocation or fracture), and tumors.


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.

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

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

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. 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.




Unlisted procedure, spine [when specified as insertion of a non-pedicle interspinous process fixation device]



ICD-10 Procedure



For the following procedures when specified insertion of a non-pedicle interspinous process fixation device:


Insertion of interspinous process spinal stabilization device into cervicothoracic vertebral joint, open approach


Insertion of interspinous process spinal stabilization device into thoracic vertebral joint, open approach


Insertion of interspinous process spinal stabilization device into lumbar vertebral joint, open approach


Insertion of interspinous process spinal stabilization device into lumbosacral joint, open approach



ICD-10 Diagnosis



All diagnoses


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.
  3. Kim DH, Shanti N, Tantorski ME, et al. Association between degenerative spondylolisthesis and spinous process fracture after interspinous process spacer surgery. Spine J. 2012a; 12(6):466-472.
  4. Kim HJ, Bak KH, Chun HJ, et al. Posterior interspinous fusion device for one-level fusion in degenerative lumbar spine disease: comparison with pedicle screw fixation - preliminary report of at least one year follow up. J Korean Neurosurg Soc. 2012b; 52(4):359-364.
  5. Lopez AJ, Scheer JK, Dahdaleh NS, et al. Lumbar spinous process fixation and fusion: a systematic review and critical analysis of an emerging spinal technology. Clin Spine Surg. 2017; 30(9):E1279-E1288.
  6. Sclafani JA, Liang K, Ohnmeiss DD, Gordon C. Clinical outcomes of a polyaxial interspinous fusion system. Int J Spine Surg. 2014; 8.

Government Agency, Medical Society, and Other Authoritative Publications:

  1. North American Spine Society (NASS). NASS Coverage Policy Recommendations. Interspinous fixation with fusion. May 2014. For additional information, visit the NASS website: Accessed on April 20, 2018.
  2. U.S. Food and Drug Administration. 510(k) Premarket Notification Database. Product Codes: KWP, KWQ, MNH, MNI, and PEK. Available at: Accessed on April 20, 2018.
  3. U.S. National Institutes of Health. Available at: Accessed on April 20, 2018.
Websites for Additional Information
  1. U.S. National Library of Medicine. Medline Plus. Health topics. Spinal fusion. Available at: Accessed on April 20, 2018.

Affix® Next Gen Spinous Process Plate System
Aileron® Interspinous Fixation System
Aspen Spinous Process Fixation System
Aurora Spine ZIP™ MIS Interspinous Fusion System
Axle™ Interspinous Fusion System
BacFuse® Spinous Process Fusion Plate
BridgePoint™ Spinous Process Fixation System
CD HORIZON SPIRE Z Spinal Fixation System
coflex-F® Implant System
InterBRIDGE® Interspinous Posterior Fixation System
Minuteman G3 Interspinous Interlaminar Fusion Device
Octave™ Posterior Fusion System
PrimaLOK SP Interspinous Fusion System
SP-Fix® Spinous Process Fixation Plate
Spinal Simplicity Spinous Process Fixation (SPF) Plate
StabiLink® MIS Interspinous Fixation System
VertiFlex® 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.

Document History






Medical Policy & Technology Assessment Committee (MPTAC) review. The document header wording updated from “Current Effective Date” to “Publish Date.” Updated Rationale, References, Websites for Additional Information, and Index sections.



MPTAC review. Updated Rationale, References, and Websites for Additional Information sections.



MPTAC review. Updated Rationale, References, Websites for Additional Information, and Index sections. Removed ICD-9 codes from Coding section.



MPTAC review. Updated Rationale, References, Websites for Additional Information, and Index sections.



MPTAC review. Revised Subject and investigational and not medically necessary statement, clarifying content to address the use of interspinous “process” fixation devices. Updated Description, Rationale, Background, and References sections.



MPTAC review. Updated Description, Rationale, Background, Definitions, References, Index and Websites for Additional Information sections.



MPTAC review. Updated Description, Rationale, and Background sections. Index updated with the StabiLink MIS Spinal Fixation System and VertiFlex Spinous Process Fixation Plate devices.



Updated Index section with the Aileron Interspinous Fixation System.



Updated Index section with the coflex-F implant device.



MPTAC review. Initial document development.