Lumbar Zygapophysial Joint Nerve (Medial Branch) Injection—Oblique Approach: Fluoroscopic Guidance

Abstract

The fluoroscopically guided lumbar medial branch block will be described using the oblique view as the trajectory view, and needle placement is confirmed in the anteroposterior view. The oblique approach is the most convenient and the least technically demanding, and it allows one to accurately and consistently reach the target point.

Keywords

back pain, facet, facet joint nerve, fluoroscopy, lumbar, lumbosacral, medial branch, spondylosis, zygapophysial joint, zygapophysial joint nerve

Note: Please see pages ii , iii for a list of anatomic terms/abbreviations used throughout this book.

The fluoroscopically guided lumbar medial branch block will be described using the oblique view as the trajectory view, and needle placement is confirmed in the anteroposterior view. The oblique approach is the most convenient and the least technically demanding, and it allows one to accurately and consistently reach the target point.

This oblique (trajectory) view is one of the multiplanar views used to guide needle placement. With well-defined target points and needle trajectories required to provide specific anesthetization of the zygapophysial joint, the volume of local anesthetic injected should be limited to 0.4 to 0.5 ml to maintain the diagnostic specificity of the injection.

Trajectory View

▪

Confirm the level (with the anteroposterior view).
▪

Tilt the fluoroscope’s image intensifier to line up the vertebral superior end plate of the targeted segment.
▪

Oblique the C-arm image intensifier ipsilaterally to form the “Scotty dog” and optimize visualization of the junction of the transverse process and superior articular process.
▪

For the L1 to L4 medial branches, the target needle destination is the junction of the superior articular process and transverse process, where the target nerve crosses midway between the superior border of the transverse process and mamillo-accessory ligament (MAL) notch. This is often described as just superior to the “eye of the Scotty dog.”
▪

For the L5 dorsal ramus, the target nerve is not the medial branch but rather the L5 dorsal ramus. This nerve courses over the ala of the sacrum on a path similar to the L1 to L4 medial branches. However, the MAL at the S1 bony segment is rudimentary.
▪

The L5 dorsal ramus target point is located at the middle of the base of the superior articular process, and therefore, slightly below the sacral ala. If the iliac crest interferes with the placement of the needle at the L5 dorsal ramus, oblique the fluoroscope 5 to 10 degrees back toward anteroposterior to visualize a non-obstructed trajectory to the junction of the superior articular process and sacral ala.
▪

Both of the nerves that innervate each targeted lumbar zygapophysial joint will need to be anesthetized.
▪

The needle should be placed parallel to the fluoroscopic beam in this trajectory view.
▪

The zygapophysial joint capsule is adjacent to the medial border of the superior articular process. As a result of joint capsule redundancy, it is possible to have intraarticular flow if the needle is medial to the optimal target point. Intraarticular flow can complicate the diagnostic specificity of the injection and more so if there is epidural leakage from the medial capsule.