Objective: To evaluate the pattern and flow of epidural contrast in fluoroscopically guided lumbar interlaminar steroid injections.
Design and methods: A prospective case series of 25 (twenty-five) consecutive patients receiving 25 (twenty-five) injections. Patients had either lumbar spinal stenosis (LSS) or herniated nucleus pulposus (HNP). All patients received their injection using a loss of resistance technique. Once the epidural space was felt localized 0.5 mL of Isovue contrast was injected to confirm accurate needle placement. If in the epidural space, another 4.5 mL was injected for a total of 5 mL contrast media. Both AP and lateral radiographs were obtained and reviewed by a physician trained in fluoroscopic injections for review of the contrast pattern. Patterns recorded were Unilateral, Bilateral, Ventral or Dorsal. The dorsal flow was also characterized as being cephalad or caudad and the number of lumbar intervertebral levels of flow were recorded as well.
Results: Dorsal contrast flow occurred in all 25 injections. Thirty-six percent (9 out of 25) resulted in ventral spread of contrast. Eighty-four percent (21 out of 25) of the injections had flow of contrast unilaterally and 16% (4 out of 25) was bilateral. The mean number of levels of flow of contrast cephalad from the injection site was 1.28 and caudally 0.88. There was a significant difference in more cephalad than caudal contrast flow (P = 0.004)
Conclusion: Thirty six percent of the injections observed in the study revealed ventral contrast flow. Bilateral contrast flow occurred in 16% of the injections. Caudad contrast flow is less than cephalad. The observed contrast flows need to be studied clinically to determine if this can affect clinical outcome.