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