Dispersal Pattern of Injectate after Lumbar Interlaminar Epidural Spinal Injection Evaluated with Computerized Tomography

Study Design Retrospective analysis of lumbar computed tomographic epidurograms. Objective To evaluate the dispersal pattern of injectate after interlaminar lumbar epidural steroid injections. Summary Prior studies have evaluated the dispersal patterns of injectate after lumbar epidural steroid injections using fluoroscopy with varying results. To date, there have been no studies evaluating the dispersal pattern utilizing computerized tomography. Methods Ten epidurograms were analyzed after lumbar interlaminar epidural steroid injection. The epidurograms were examined, evaluating the dispersal pattern in longitudinal flow as well as circumferential flow. In addition, pain values were assessed with the visual analogue scale. Results Mean diffusion in the rostral direction was 9.8 cm (standard deviation 4.0 cm, range 4.0 to 15.0 cm). Mean diffusion in the caudal direction was 5.4 cm (standard deviation 1.4 cm, range 3.0 to 8.0 cm). Both rostral and caudal flow had a p value < 0.001. The circumferential flow was 360 degrees in 9 of 10 cases. In addition, there was significant (p = 0.006) reduction in pain. Conclusion Interlaminar lumbar epidural steroid injections are an effective treatment modality for various spine-related conditions. The injectate diffuses throughout the epidural space with nearly uniform circumferential flow as well as significant rostral and caudal flow.