Comparison of Epidural Spreading Patterns and Clinical Outcomes of Transforaminal Epidural Steroid Injection with High-Volume Injectate via the Subpedicular Versus the Retrodiscal Approach

Abstract

Background: The effect of transforaminal epidural steroid injection (TFESI) appears to be influenced by the volume of the injected material because there is a positive correlation between injection volume and extent of pain relief. Objectives: The purpose of this study was to examine how many vertebral segments are covered by the subpedicular (SP) approach and the retrodiscal (RD) approach and to compare the clinical outcomes of the 2 approaches in TFESI with high-volume injectates. Study Design: A randomized, active control trial. Setting: Medical University centers. Methods: Fifty patients were randomly assigned to either the SP group or the RD group. TFESI was performed with high-volume injectates. A total of 9 mL injectate was divided into 3 injections (0.5 mL, 2.5 mL, and 6 mL) given at 10-second intervals. The primary outcome measure was injectate distribution. The spreading patterns were described as unilateral, bilateral, ventral, or dorsal. Ventral or dorsal flow was also described as being cephalad or caudad, respectively. The secondary outcome measures were pain relief and reduction of functional disability at 4 weeks after the procedure. Results: The total numbers of vertebral segments and median levels of contrast spread from the injection site were not significantly different between the 2 groups. However, in 3 mL of injectate, the injectate spread showed more extensive bilateral distribution in the RD group. At 4 weeks after treatment, both groups demonstrated statistically significant pain relief and improvement in functional status. No significant differences were observed between the 2 groups. Limitations: We enrolled only a small number of patients and did not analyze long-term outcomes. Patients with severe spinal stenosis or herniated nucleus pulposus were included. Slightly different methods were used in the 2 groups to determine the number of levels at which the injectate was spread. Conclusions: Epidural spreading patterns and clinical outcomes of lumbar TFESI with highvolume injectate were not significantly different between the SP approach and the RD approach. Institutional Review Board (IRB) approval: Institutional Review Board of Ewha Womans University Hospital (EUMC 2015-05-003-003). Clinical trials registration number: Clinical Research Information Service (CRIS, registration number: KCT0002288; RCT URL: https://cris.nih.go.kr/cris/ search/search_result_st01.jsp?seq=7309) Key words: Epidural injections, epidural space, low back pain, radiating pain, disability evaluation, steroids, local anesthetics, intervertebral disc disease, spinal stenosis