A Differential Clinical Benefit Examination of Full Lumbar Endoscopy vs Interspinous Process Spacers in the Treatment of Spinal Stenosis: An Effect Size Meta-Analysis of Clinical Outcomes

Abstract

Study design: A design-agnostic standardized effect meta-analysis of 48 randomized, prospective, and retrospective studies on clinical outcomes with spinal endoscopic and interspinous process spacer (IPS) surgery.

Objective: The study aimed to provide reference set of Oswestry Disability Index (ODI) and visual analog scale (VAS) effect size data for back and leg pain following endoscopic and IPS decompression for lumbar herniated disc, foraminal, or lateral recess spinal stenosis.

Background: Mechanical low back pain following endoscopic transforaminal decompression may be more reliably reduced by simultaneous posterior column stabilization with IPS.

Methods: A systematic search of the PubMed, EMBASE, Web of Science, and the Cochrane Central Register of Controlled Trials from 1 January 2000 to 2 April 2020, identified 880 eligible endoscopy and 362 IPS studies varying in design and metrics. The authors compared calculated standardized effect sizes (Cohen's d) for extracted ODI, VAS-back, and VAS-leg data.

Results: The pooled standardized effect size combining the ODI, VAS-back, and VAS-leg data for the total sample of 19862 data sets from the 30 endoscopy and 18 IPS was 0.877 (95% CI = 0.857-0.898). When stratified by surgery, the combined effect sizes were 0.877 (95% CI = 0.849-0.905) for endoscopic decompression and 0.863 (95% CI = 0.796-0.930; P = 0.056) for IPS implantation. The ODI effect sizes calculated on 6462 samples with directly visualized endoscopic decompression were 0.917 (95% CI = 0.891-0.943) versus 0.798 (95% CI = 0.713-0.883; P < 0.001) with indirect IPS decompression (P < 0.001). The VAS-back effect sizes calculated on 3672 samples were 0.661 (95% CI = 0.585-0.738) for endoscopy and 0.784 (95% CI: 0.644-0.923; P = 0.187) for IPS. The VAS-leg effect sizes calculated on 7890 samples were 0.885 (95% CI = 0.852-0.917) for endoscopic decompression and 0.851 (95% CI = 0.767-0.935; P = 0.427).

Conclusion: Lumbar IPS implantation produces larger reduction in low back pain than spinal endoscopy. On the basis of this meta-analysis, the combination of lumbar transforaminal endoscopy with simultaneous IPS has merits and should be formally investigated in higher grade clinical studies.

Clinical relevance: Meta-analysis on the added clinical benefit of combining lumbar endoscopic decompression with an interspinous process spacer.

Keywords: herniated disc; interspinous process spacer; lumbar endoscopy; meta-analysis; spinal stenosis.

Figure 1

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses flowchart of selected endoscopy and interspinous process spacer studies. ODI, Oswestry Disability Index; VAS, visual analog scale.

Figure 2

Forest plot of calculated Oswestry Disability Index (ODI) effect sizes (ES), 95% CI, and the number of patients enrolled in each of the endoscopic spinal surgery and interspinous process spacer (IPS) studies listed in alphabetical order according to the first author’s name. The number of individual study patients is represented by the size of the square. The calculated pooled standardized ES for changes in ODI for the endoscopy studies was 0.917 (95% CI = 0.891–0.943). The corresponding ES for the IPS procedures was 0.798 (95% CI = 0.713–0.883). The analysis of variance Q test of difference showed a statistically higher ODI ES with endoscopy than with the IPS procedure (P = 0.001). Prometa 3 plotted the ES data in terms of non-standardized differences.

Figure 3

Forest plot of calculated visual analog scale (VAS)-back effect sizes (ES), 95% CI, and the number of patients enrolled in each of the endoscopic spinal surgery and interspinous process spacer (IPS) studies listed in alphabetical order according to the first author’s name. The number of individual study patients is represented by the size of the square. The calculated pooled standardized ES for changes in VAS-back for the endoscopy studies was 0.661 (95% CI = 0.585–0.738). The corresponding ES for the IPS procedures was 0.784 (95% CI = 0.644–0.923). The analysis of variance Q test of difference indicated that this difference in VAS-back ES was not statistically significant (P = 0.187). Prometa 3 plotted the ES data in terms of non-standardized differences.

Figure 4

Forest plot of calculated visual analog scale (VAS)-leg effect sizes (ES), 95% CI, and the number of patients enrolled in each of the endoscopic spinal surgery and interspinous process spacer (IPS) studies listed in alphabetical order according to the first author’s name. The number of individual study patients is represented by the size of the square. The calculated pooled standardized ES for changes in VAS-leg for the endoscopy studies was 0.885 (95% CI = 0.852–0.917). The corresponding ES for the IPS procedures was 0.851 (95% CI = 0.767–0.935). The analysis of variance Q test of difference indicated that this difference in VAS-leg ES was not statistically significant (P = 0.427).

Figure 5

Meta-analysis regression plot of effect size vs age in years using random effects model showed no significant correlation (P = 0.289).

Figure 6

Meta-analysis plot of effect size (ES) vs follow-up in months using random effects model showed a statistically significantly higher proportion of studies (all of the interspinous spacer studies) with either 24 months follow-up or more with higher ES numbers in the longer follow-up studies (P = 0.026).

Figure 7

Funnel plot assessing publication bias (SE vs effect size).