Impact of Transforaminal Epidural Steroid Injection on Pain and Disability Outcomes by Lumbar Intervertebral Disc Herniation Class: A Prospective Study

Abstract Background Lumbosacral radicular pain significantly affects daily life activities and is typically caused by nerve root compression owing to disc herniation. Transforaminal epidural steroid injection (TFESI) is a prevalent treatment modality; however, the impact of varying disc morphologies on treatment outcomes remains unclear. The aim of this study was to evaluate the effects of TFESI on pain and disability across different lumbar disc morphologies using the Michigan State University (MSU) classification system. Methods This prospective cohort study enrolled 168 patients with single-level lumbar disc herniation at L4-L5 or L5-S1 treated with TFESI. Patients were divided into seven subgroups according to the MSU classification based on MRI findings. The Numerical Rating Scale (NRS) for pain and Oswestry Disability Index (ODI) for assessing disability were measured at baseline, 1-month and 3-months post-procedure. Results TFESI significantly reduced NRS and ODI scores in all groups (p < 0.001). At 1-month follow-up, NRS scores of group 1B were significantly lower than those of groups 2A and 2AB (p < 0.001 and p = 0.020, respectively); at the 3-month follow-up, no differences were observed between the groups. Although ODI scores improved over time, they did not exhibit significant differences among the subgroups throughout the study period. Conclusion TFESI effectively reduces pain and disability across varying disc morphologies. At the 1-month mark, pain relief was more pronounced in group 1B compared to 2A and 2AB groups, whereas at the 3-month mark, the results were similar between subgroups. Larger studies with longer follow-up are needed to improve patient selection criteria and optimize treatment strategies. Data sharing statement This study was registered at ClinicalTrials.gov under the identifier (NCT06275529)