A comparative systematic review and meta-analysis of 3 routes of administration of epidural injections in lumbar disc herniation

Background: The Best Practices in Pain Management from the U.S. Department of Health and Human Services (HHS) describes interventional techniques as part of a continuum. Epidural injections are commonly utilized modalities in managing low back and lower extremity pain. Epidural injections were initially administered in 1901 where the first descriptions of caudal epidural with local anesthetic for low back pain appeared. Since then, multiple developments have occurred. Currently, epidural injections are provided by caudal, interlaminar, and transforaminal approaches. The comparative effectiveness of each modality has been studied. However, comparative assessment has been sparse. Objectives: To assess the efficacy of 3 routes of administration of epidural injections for lumbar disc herniation. Study Design: A systematic review and meta-analysis of randomized controlled trials (RCTs) of transforaminal, interlaminar and caudal epidural injections in managing chronic low back and lower extremity pain due to lumbar disc herniation. Methods: RCTs with a placebo control or an active control design, performed under fluoroscopic guidance, with at least 6 months of follow-up are included. The outcome measures were pain relief and functional status improvement. Significant improvement was defined as 50% or greater pain relief and functional status improvement. Data extraction and methodological quality assessment were performed. Evidence was summarized utilizing principles of best evidence synthesis. Results: A total of 21 trials were included. Of these, 7 studied caudal epidural injections, whereas transforaminal epidural injections were studied in 12 trials, and lumbar interlaminar epidural injections were studied in 10 trials, which all met inclusion criteria. Based on qualitative and quantitative analysis, which included conventional dual-arm and single-arm analysis for interlaminar epidural injections, and single-arm analysis for caudal and transforaminal epidural injections, and the approach to the epidural space, there is Level I evidence for local anesthetic and steroids, Level II for local anesthetic alone for transforaminal and interlaminar approaches, and Level II for the caudal approach with steroids or local anesthetic alone for short-and long-term relief. Limitations: There is a paucity of literature with intermediate or long-term relief of at least 6 months with appropriate outcome parameters. Conventional dual-arm meta-analysis was feasible only for interlaminar epidural injections. Conclusion: Epidural injections with local anesthetic and steroids showed Level I evidence for transforaminal and interlaminar approaches, whereas with local anesthetic alone Level II evidence was demonstrated. In contrast, caudal epidural injections showed Level II evidence with local anesthetic with steroids or local anesthetic alone.