Injectate Volumes Needed to Reach Specific Landmarks in S1 Transforaminal Epidural Injections

Abstract

Objectives. We identify the contrast volumes needed to reach specific landmarks during S1 transforaminal epidural injections (S1-TFEIs). Design. Prospective, nonrandomized, observational human study. Setting. Academic/private pain management practice. Subjects. Forty-two patients undergoing S1-TFEIs were investigated. Thirty-seven patients were included in this study. Interventions. S1-TFEIs were performed using contrast-enhanced fluoroscopic visualization. Main Outcome Measurements. After confirming appropriate spinal needle position, up to 5mL of nonionic contrast was slowly injected. Under biplanar fluoroscopic guidance, contrast volumes were recorded as flow reached specific anatomic landmarks: the ipsilateral S1 pedicle, the superior aspect of the L5-S1 disc space, and across the midline of the spinous process. Results. After injecting 2mL of contrast, 100% of S1-TFEIs spread to the medial aspect of the ipsilateral superior pedicle of S1. After injecting 3.0mL of contrast, 92% of S1-TFEIs spread to the superior aspect of the L5-S1 intervertebral disc. After injecting 4mL of contrast, 27% of S1-TFEIs spread beyond the midline of the spinous process, but by only a few millimeters. Conclusions. This study demonstrates injectate volumes needed to reach specific anatomic landmarks in S1-TFEIs. A volume of 3.0mL of contrast reaches the superior aspect of the L5-S1 intervertebral disc 92% of the time. © 2012 Wiley Periodicals, Inc.