Standalone anteroposterior contrast spread pattern is insufficient to distinguish lumbar epidural from extradural spread: A prospective study.

Background: There is debate about whether a standalone anteroposterior (AP) view can distinguish epidural contrast from non-epidural contrast spread.

Objectives: This study aims to assess the accuracy of the AP (anteroposterior) and Contralateral Oblique (CLO) views in distinguishing epidural contrast spread patterns from non-epidural contrast spread patterns.

Methods: Patients undergoing lumbar epidural steroid injections consented to participate in the study. A 20-gauge Tuohy needle was advanced very close to the epidural space, and 0.5-1 ml of contrast was then injected. CLO, AP, and lateral images of non-epidural spread were saved. The AP and CLO images were randomly mixed with images from historical controls with actual epidural spread.

Results: A total of 24 false epidurograms in the AP and CLO views were mixed with an equal number of true epidurograms, resulting in 48 images each in the AP and the CLO views, respectively. Among the cohort of 10 experienced interventional pain physicians, the mean accuracy of correctly identifying epidural spread as epidural using the AP view alone was 51 % (SD 19 %). In addition, the accuracy of correctly identifying non-epidural spread as non-epidural using the AP view alone was 64 % (SD 15 %). Cohen's Kappa was 0.15, indicating minimal agreement between the interventionalists. In contrast, the mean accuracy of correctly identifying epidural spread as epidural using the CLO view alone was 99 % (SD 2 %). In addition, the accuracy of correctly identifying non-epidural spread as non-epidural using the CLO view alone was 96 % (SD 9 %). Excluding one outlier, the accuracy for the rest of the reviewers in determining non-epidural spread as non-epidural was 99 %. Cohens' Kappa was 0.95, indicating a high degree of agreement between the interventionalists.

Conclusion: This study reveals that utilizing a standalone AP view without a CLO view was inadequate to distinguish epidural from non-epidural spread. Specifically, our study supports the continued use of CLO depth views to identify epidural contrast spread correctly.