Factors associated with improved outcomes after lumbar transforaminal epidural steroid injections for radicular pain: A systematic review.

Purpose: Despite numerous studies, the factors contributing to clinical success after a lumbar transforaminal epidural steroid injection (LTFESI) for radicular pain remain unclear. The aim of this study was to systematically review literature evaluating preprocedural predictive factors for improved outcomes in patients receiving a LTFESI. Methods: We searched databases including PubMed/MEDLINE, Cochrane Library, and Scopus for studies published from 2006 through 2023. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed to identify articles evaluating prognostic factors associated with outcomes after a LTFESI. Studies were excluded if articles treated patients with axial back pain or if they were not performed under imaging guidance with contrast medium. The quality of included studies was appraised by 2 reviewers using the Quality in Prognosis Studies tool (QUIPS). Results: Eighteen studies met eligibility criteria which evaluated prognostic factors across domains including patient characteristics, clinical findings, magnetic resonance imaging (MRI) characteristics, anatomical variations, and electromyography findings. The largest predictive factor studied were the MRI findings causing radicular pain. A lower grade of nerve compression and a lumbar disc herniation which was central, foraminal or extraforaminal was associated with improved outcomes, as opposed to a subarticular location. Lower paraspinal mapping scores on electromyography were correlated with better outcomes than higher scores. Outcomes were not affected if a lumbar disc herniation was accompanied by degenerative changes or if the cause of radicular pain was from a lumbar disc herniation or from lumbar spinal stenosis. The risk of bias across many domains in the studies were varied being highest overall in the domains of study attrition and study confounding. Conclusions: The evidence behind factors that predict outcomes from a lumbar transforaminal epidural steroid injection have varying degrees of bias, but trends appear that can be used to guide clinical decision making.