Objective: To evaluate the pattern and spread of epidural contrast during fluoroscopically guided lumbar transforaminal epidural steroid injections.

Design: A prospective study of case series of 20 consecutive patients receiving lumbar transforaminal epidural injections.

Methods: Patients had either herniated nucleus pulposus or lumbar spinal stenosis. All patients received their injection by one of five physicians trained in this technique. Once the needle tip was felt to be in the anterior epidural space anteroposterior and a lateral radiographs were obtained after a total of 2 mL of iopamidol (Isovue) contrast was injected. Epidurograms were reviewed by a physician trained in fluoroscopic injections. Patterns were recorded as unilateral, bilateral, dorsal or ventral. Ventral flow, both cephalad and caudal, and number of lumbar intervertebral levels of flow were recorded as well.

Results: Ventral contrast flow occurred in all 20 injections. Unilateral contrast flow was noted in all injections. The mean number of levels of flow of contrast cephalad and caudad from the injection site were 1.13 and 0.6 levels, respectively, but these differences were not statistically significant. There were no significant differences in contrast flow noted between patients with herniated nucleus pulposus or lumbar spinal stenosis. Vascular injection patterns were noted with 2 injections, which required repositioning of the needles.

Conclusion: Contrast appeared ventrally and unilaterally in all injections. Dorsal flow occurred in 20% of these injections. No contrast flow crossed the midline. The observed contrast flow patterns should be studied clinically to determine whether they have any effect on clinical outcome. Intravascular injections were noted in 10% of cases.

Keywords: Epidural injections, transforaminal epidural injections, herniated nucleus pulposus, lumbar spinal stenosis, fluoroscopy