Reliability and Safety of Contra-Lateral Oblique View for Interlaminar Epidural Needle Placement

Cord trauma is a risk with a cervical and thoracic interlaminar epidural approach to the epidural space. Intermittent lateral fluoroscopic imaging to detect needle depth is often cumbersome and may be difficult to interpret. In comparison, the contra-lateral oblique (CLO) fluoroscopic view is efficient and easy to interpret. However, the in vivo reliability and safety of this technique has not been formally investigated.The senior author collected fluoroscopic images on 278 consecutive patients undergoing an interlaminar epidural block at the T1-T2 level performed using a 17 gauge Tuohy needle. Before catheter placement, anterior-posterior (AP) and CLO fluoroscopic images were saved with the needle at the ligamentum flavum and the needle just through the ligamentum flavum.We randomly selected the images of 40 cases that included the paired CLO images (total 80 images) documenting the views at and through the ligamentum flavum. Three interventionalists were asked to review, in a blinded fashion, the randomly selected, paired CLO images and to score each image, recording whether the 17 gauge needle was in or out of the epidural space to determine the accuracy and reliability of this technique.There was a 97.5%, 95%, and 93.8% agreement between each reviewing physician and the senior author resulting in a correlation using the Kappa statistic value of 0.950, 0.875, and 0.874, respectively (P < 0.001). The 3 reviewing physicians disagreed with the senior author's correct answer in 2.5%, 5%, and 6.2%, respectively, however, the disagreement occurred primarily because of poor image quality. Agreement between the 3 reviewing physicians was 93.8%, 96.3%, and 90%, with a Kappa value of 0.875, 0.924, and 0.799, respectively (P < 0.001). There was 100% technical success in the 278 case series without "wet taps," provocation of pain during entry, or any other immediate post procedural complication.We conclude the CLO view provides an efficient and reliable method to visualize needle tip depth in relation to the epidural space. The close inter-observer agreement was possible with minimal physician instruction.Key words: Cervical interlaminar, cervical epidural, contra-lateral oblique, fluoroscopic imaging.