Nancy E. Epstein1, Marc A. Agulnick2
  1. Professor of Clinical Neurosurgery, School of Medicine, State University of NY at Stony Brook, c/o Dr. Marc Agulnick, 1122 Franklin Avenue Suite 106, Garden City, NY, USA,
  2. Assistant Clinical Professor of Orthopedics, NYU Langone Hospital, Long Island, NY, USA, 1122 Frankling Avenue Suite 106, Garden City, NY, USA.

Correspondence Address:
Nancy E. Epstein, M.D., F.A.C.S., Professor of Clinical Neurosurgery, School of Medicine, State University of NY at Stony Brook, and Editor-in-Chief of Surgical Neurology International NY, USA, and c/o Dr. Marc Agulnick, 1122 Franklin Avenue Suite 106, Garden City, NY, USA.


Copyright: © 2024 Surgical Neurology International This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-Share Alike 4.0 License, which allows others to remix, transform, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.

How to cite this article: Nancy E. Epstein1, Marc A. Agulnick2. Perspective: Efficacy and outcomes for different lumbar interspinous devices (ISD) vs. open surgery to treat lumbar spinal stenosis (LSS). 19-Jan-2024;15:17

How to cite this URL: Nancy E. Epstein1, Marc A. Agulnick2. Perspective: Efficacy and outcomes for different lumbar interspinous devices (ISD) vs. open surgery to treat lumbar spinal stenosis (LSS). 19-Jan-2024;15:17. Available from:

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Background: Interspinous devices (ISD) constitute a minimally invasive (MI) alternative to open surgery (i.e., laminectomy/decompression with/without fusion (i.e., posterior lumbar interbody fusion (PLIF)/posterolateral instrumented fusion (PLF)) for treating lumbar spinal stenosis (LSS). Biomechanically, static and/or dynamic ISD “offload” pressure on the disc space, increase intervertebral foraminal/disc space heights, reverse/preserve lordosis, limit range of motion (ROM)/stabilize the surgical level, and reduce adjacent segment disease (ASD). Other benefits reported in the literature included; reduced operative time (OR Time), length of hospital stay (LOS), estimated blood loss (EBL), and improved outcomes (i.e., ODI (Oswestry Disability Index), VAS (Visual Analog Scale), and/or SF-36 (Short-Form 36)).

Methods: Various studies documented the relative efficacy and outcomes of original (i.e., Wallis), current (i.e., X-STOP, Wallis, DIAM, Aperius PercLID), and new generation (i.e., Coflex, Superion Helifix, In-Space) ISD used to treat LSS vs. open surgery.

Results: Although ISD overall resulted in comparable or improved outcomes vs. open surgery, the newer generation ISD provided the greatest reductions in critical cost-saving parameters (i.e., OR time, LOS, and lower reoperation rates of 3.7% for Coflex vs. 11.1% for original/current ISD) vs. original/current ISD and open surgery. Further, the 5-year postoperative study showed the average cost of new generation Coflex ISD/decompressions was $15,182, or $11,681 lower than the average $26,863 amount for PLF.

Conclusion: Patients undergoing new generation ISD for LSS exhibited comparable or better outcomes, but greater reductions in OR times, EBL, LOS, ROM, and ASD vs. those receiving original/current ISD or undergoing open surgery.

Keywords: Interspinous Devices (ISD), Static, Dynamic, X-Stop, Coflex, Lumbar Spinal Stenosis (LSS), Decompression, Posterior Lumbar Interbody Fusion (PLIF), Posterolateral Fusion (PLF), Open Surgery, Laminectomy, Complications, Outcomes, Adverse Events


For treating lumbar spinal stenosis, we compared the efficacy and outcomes of 3 different categories of interspinous devices (ISD) vs. open surgery (i.e., laminectomy/decompression, posterior lumbar interbody fusion (PLIF), posterolateral fusion (PLF/other) [ Tables 1 and 2 ].[ 1 - 15 ] The three categories of ISD included; the original (i.e., Wallis), current (i.e., X-STOP, Wallis, DIAM, Aperius PercLID), and new generation (i.e., Coflex, Superion Helifix, In-Space) ISD. Biomechanically, ISD devices were designed to; “off-load” the pressure on the disc space, increase intervertebral foraminal/disc space height, reversed/preserve the lumbar lordosis, limit range of motion (ROM)/stabilize the index surgical level, and decrease the incidence of adjacent segment disease (ASD). We also reviewed the literature regarding additional reported benefits; reduced operative times (OR Time), shorter lengths of stay (LOS), decreased estimated blood loss (EBL), fewer reoperations, lesser perioperative/postoperative costs, and comparable vs. improved outcomes (i.e., ODI (Oswestry Disability Index), VAS (Visual Analog Scale), and/or SF-36 (Short Form-36).

Table 1:

Utility of Coflex devices vs. decompressions vs. other fusions in dealing with lumbar spinal stenosis.


Table 2:

List of interspinous and interlaminar stabilization and distraction devices.


Biomechanically, ISD Enhance Stability at the Index Surgical Level with Reduction of ASD

Five biomechanical studies using surgical fusion models documented the efficacy of different ISD devices in reducing ROM at the index and adjacent surgical levels [ Tables 1 and 2 ].[ 1 , 4 , 5 , 10 , 12 ] In 6 human cadavers, Hirsch et al. (2015) evaluated foraminal surface areas in flexion/extension (i.e., using a spinal loading frame, testing flexion/extension from 0-10 Nm, marking L34, L45, and L5S1 foramina, employing Stereoscopic 3D images before/after implants) placed in In-space, X-STOP, DIAM, and Wallis ISD at L45; “All four devices significantly opened the L45 foramen in extension”, but for the X-Stop(®) and In-space(®) devices the;“... L4-L5 foramen opened not only in extension but also in flexion and the neutral position.”[ 5 ] Using six human male cadaver biomechanical models, Che et al. (2016) studied 1-level rigid fixation with kinematics/intradiscal pressure recordings with 3-dimensional motion/applied loads in flexion-extension, lateral bending, and axial rotation.[ 1 ] They found that L4-L5 pedicle screw-rod fixation (PSRF)/L3-L4 Coflex devices stabilized both levels, while the PSRF at L4-L5 stabilized L4-L5, but increased L3-L4 ROM; they concluded that future Coflex devices could fuse index surgical levels, and reduce the frequency of ASD [ Tables 1 and 2 ].[ 1 ] In 2019, Shen et al. performed a “biomechanical analysis” (i.e., “finite element study”) of “intradiscal pressure (IDP) and facet joint force (FJF)” using 4 ISD devices (i.e., Coflex-F, DIAM, Wallis, and Pedicle Screws) placed at L3-L4; all ISD significantly decreased ROM at the index surgical level in flexion/extension, but exhibited “little influence” in torsion/ lateral bending.[ 12 ] Notably, the Coflex-F device; “...showed advantages in stabilizing the surgical level...” and demonstrated a greater reduction of ASD vs. Wallis and DIAM devices. Guo et al. in 2022 looked at 4 CT-derived radiographic studies (i.e., including “flexion, extension, lateral bending, and rotation for normal lumbar CT, mild degenerated lumbar segment, Coflex, and X-Stop fixed lumbar segments) to; “.compare ROM, intradiscal pressure, facet joint force, maximum Von Mises stress, and peak facet contact forces.[ 4 ] They found; “Coflex and X-STOP devices can effectively decrease the ROM and intradiscal pressure in extension, without affecting the adjacent levels” [ Tables 1 and 2 ]. In the same year, Liu et al. (2022) performed a biomechanical analysis in flexion, extension, lateral bending/axial rotation, and ROM with CT images of LSS utilizing four finite element (FE) models from L3-S5 (i.e., including the intact lumbar spine, and BacFuse, X-Stop and Coflex ISD devices); although all 3 ISD decreased ROM in extension, the BacFuse ISD further increased cephalad stress, the Coflex ISD increased distal stress, and the X-STOP ISD placed maximal stress at the index/surgical levels.[ 10 ]

Treatment of LSS: Efficacy and Outcomes for Different ISD Devices vs. Open Surgery

For LSS, Efficacy and Outcomes of Different ISD Devices vs. No Surgery vs. Open Surgery

Multiple ISD devices used to treat LSS improved clinical outcomes [ Tables 1 and 2 ].[ 6 , 8 , 14 ] Trautwein et al. (2010) assessed the neutral, flexion, and extension X-rays for 176 patients undergoing Coflex placement for LSS; they observed extremely rare Coflex “fatigue failure.”[ 14 ] Kabir et al. (2010) found that X-STOP, Coflex, Wallis, and DIAM ISD devices improved clinical outcomes vs. poorer results seen for patients not undergoing any surgery.[ 6 ] In 10 studies, Li et al. (2017) found that new-generation Coflex ISD yielded better ODI but comparable VAS outcomes, shorter LOS, greater reductions in EBL, and fewer complications vs. patients having open decompressions and/or fusions.[ 8 ]

For LSS, Improved Efficacy and Outcomes of Decompressions/ Coflex ISD Alone or vs. Decompressions Alone

Two series focused on the improved efficacy and outcomes for patients undergoing decompressions/Coflex ISD placement for LSS alone or vs. decompressions only [ Tables 1 and 2 ].[ 2 , 7 ] For a non-randomized series of LSS patients, Kumar et al. (2014) found better postoperative outcomes (ODI, VAS, SF-36) at six months, one year, and two years following decompressions/Coflex ISD (22 patients) placement vs. decompressions alone (24 patients; outcomes still improved but inferior to Coflex results). Further, outcomes in both patient groups did not directly correlate with improved radiological parameters (i.e., disc/foraminal height sagittal angle).[ 7 ] For 56 patients with LSS managed with decompression/Coflex ISD alone, Du et al. (2020) found postoperative outcomes at six months and nearly nine postoperative years (i.e., without intervening spinal/epidural injections or physical therapy) showed nearly comparable maintained improvement (i.e., VAS, ODI, JOA scores); over this interval there was just a slight increase in ROM at the index and adjacent levels, with only mild decreases in intervertebral disc space and foraminal height.[ 2 ] Additionally, there were only 11 overlapping complications ((19.6%): 1 surgery-related, one hematoma, one infection, one dural tear, two restenosis, one ectopic ossification, one osteolysis, one fracture, four loosening/shedding displacement, 6 ASD), with just 6 requiring reoperations (10.7%: 2 for recurrent stenosis, and 4 for ASD).

For LSS, Improved Efficacy and Outcomes of Decompressions/ Coflex ISD Alone or vs. Decompressions Alone

For LSS, four studies documented better or similar outcomes for decompressions/Coflex ISD procedures but greater reductions in perioperative factors vs. PLIF and vs. decompressions alone [ Tables 1 and 2 ].[ 3 , 5 , 9 , 11 , 14 ] Yuan et al. (2017) evaluated the 5-year clinical/radiological outcomes for 87 consecutive non-randomized or “clinically segregated” (i.e., selected/chosen) LSS patients undergoing decompressions/Coflex ISD (42 patients) vs. PLIF (45 patients) procedures.[ 15 ] Although both groups demonstrated comparable improvement on ODI and VAS outcome scales, decompression/Coflex devices showed greater reductions in EBL, LOS, operative times, and ROM (more significantly reduced with Coflex vs. PLIF procedures) and no increase in ASD vs. PLIF (i.e., likely due to the Coflex ISD “softer and less stiff ” biomechanical construct). Also in 2017, Pintauro et al. compared outcomes in 37 studies using original (i.e., Wallis), current (i.e., X-STOP, Wallis, DIAM, Aperius PercLID), and next generation (i.e., Coflex, Superion Helifix, In-Space) ISD devices; at two postoperative years clinical outcomes for all devices were comparable, but next-generation ISD required just a 3.7% incidence of reoperations vs. 11.1% for original/current devices.[ 11 ] In 2020, Fan and Zhu (2020) identified 946 patients in 10 LSS RCTs (Randomized Controlled Studies) who underwent decompressions/ Coflex ISD vs. PLIF vs. decompressions alone; although they all demonstrated improved outcomes, Coflex and PLIF patients had better VAS scores vs. decompressions alone, and Coflex patients alone sustained fewer complications vs. PLIF patients.[ 3 ] Li et al. (2023), in a meta-analysis of 26 LSS articles, showed decompressions/Coflex ISD reduced operative times, EBL, ASD, LOS, and complication rates but showed comparable long-term JOA, VAS, ODI outcomes vs. PLIF; these findings inferred potential cost-savings for utilizing Coflex ISD.[ 9 ]

Greater Cost Savings for Decompression/Coflex ISD vs. Instrumented Posterolateral Lumbar Fusions (PLF) for Treating LSS

The study by Schmier et al. focused on the cost savings for decompression/Coflex ISD vs. instrumented posterolateral lumbar fusions (PLF) for treating LSS [ Tables 1 and 2 ].[ 13 ] “(In a)...randomized, controlled, multicenter US Food and Drug Administration Investigational Device Exemption clinical trial...”, they documented the efficacy, outcomes (i.e., QALY: quality-adjusted life years), and reduced costs for performing decompression/Coflex procedures vs. instrumented posterolateral fusions (PLF). At five postoperative years, the average Medicare payments for decompression/Coflex ISD was $15,182 vs. a substantially higher $26,863 for those undergoing PLF (i.e., a cost savings of $11,681), and patients experienced higher “...mean quality-adjusted life years (i.e., 3.02 vs. 2.97)”, which equated with greater “utility.”


For treating LSS, different ISD devices (i.e., original, current, and new generation) resulted in comparable or better outcomes vs. open surgery (i.e., laminectomy/ decompressions, PLIF, instrumented PLF) or no surgery, but newer generation devices often demonstrated greater reductions in EBL, LOS, OR time, index-level ROM, ASD, reoperation rates, and increased cost savings.

Ethical approval

Institutional Review Board approval is not required.

Declaration of patient consent

Patient’s consent not required as there are no patients in this study.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation

The authors confirm that there was no use of Artificial Intelligence (AI)-Assisted Technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.


The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.


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