Effect of High-Volume Injectate in Lumbar Transforaminal Epidural Steroid Injections: A Randomized, Active Control Trial

Background: There have been many studies proving the effectiveness of lumbar transforaminal epidural steroid injections (TFESIs) for the treatment of radicular pain. Dexamethasone has been suggested as an alternative to particulate steroids. However, no controlled trials have investigated the effect of different injected volumes for a same dose of dexamethasone. Objective: To compare the effects of a high-volume injectate with those of a low-volume injectate using the same dose of dexamethasone for 2 groups in lumbar TFESI. Study Design: A prospective, randomized, active control trial. Setting: The outpatient clinic of a single academic medical center. Methods: A total of 66 patients were randomized to receive lumbar transforaminal epidural dexamethasone injections with either a low-volume injectate (3mL, N = 30) or a high-volume injectate (8mL, N = 32). The primary outcome measures for this study were the incidence of the patients achieving meaningful pain relief and a reduction on the Visual Analogue Scale (VAS, range 0 – 100) at 4 weeks after the procedure. The definition of “meaningful pain relief” was ≥ 50% from baseline. The secondary outcomes included the Roland-Morris Disability Questionnaire (RMDQ, range 0 – 24) score and adverse effects. The outcomes were assessed 4 weeks after the procedure. Results: Four weeks after the procedure, in the DL8 group, the incidence of achieving meaningful pain relief was higher compared with DL3 group (19, 59.4% vs. 9, 30%, P = 0.024). Both groups demonstrated a significant improvement in their VAS and RMDQ scores (P < 0.05). The VAS of the high-volume injectate group (DL8) was significantly lower than that of the low-volume injectate group (DL3) (33.3 ± 25 vs. 46.3 ± 25, P = 0.036). There was no significant difference in the RMDQ score between the 2 groups. Limitations: We enrolled a small number of patients and did not assess the long-term outcomes. Conclusions: Injectate at a volume of 8 mL was more effective than injectate at a volume of 3 mL for radicular pain in a lumbar transforaminal steroid injection, although both of the injectates contained the same dose of dexamethasone. Key words: Dexamethasone, disc herniation, epidural injection, lumbar, radiculopathy