Fig 1.

Epidural Injection Technique as demonstrated in a 38-year-old man with back pain.

A, CTF image demonstrates the needle to be appropriately angled toward the epidural space. This image was taken at the lower part of the posterior spinous process; opening used to access the epidural space, between the spinous process and medial facet, is clearly seen. The small triangle of posterior epidural fat is a useful landmark to aim for, although it is not present in some patients, particularly those with severe spinal stenosis.

B, The needle tip at the outer edge of the ligamentum flavum, corresponding to a feeling of resistance while advancing the needle, is shown. The tip can be identified by the shadowing artifact extending from it. Notice how the needle has avoided most of the erector spinae muscles during insertion, adding to the comfort level of the patient.

C, The final image in this study demonstrates contrast medium outlining the epidural space, tracking along the anterior edge of the ligamentum flavum. Although cross-filling is not seen on this image, it can be shown with a larger contrast medium injection, but this has been found to be unnecessary.