Lumbar Zygapophysial Joint Nerve (Medial Branch) Injection, Oblique Approach

Chapter 14 Lumbar Zygapophysial Joint Nerve (Medial Branch) Injection, Oblique Approach



Leland Berkwits, Jason G. Anderson, Michael B. Furman


Note: Please see page ii for a list of anatomical terms/abbreviations used in this book.


Lumbar medial branch blocks are diagnostic procedures that are indicated to determine whether a patient’s axial pain is caused by the zygapophysial joints under study. Medial branch blocks are used to determine if a patient is a candidate for radiofrequency neurotomy.1


The lumbar facet joints were first suggested as a source of low back and lower extremity pain by Goldthwait in 1911.2 Provocation maneuvers have been comprehensively studied in the lumbar spine, and they have widely varying sensitivity, specificity, and interrater variability.3 Schwarzer concluded that, although the lumbar zygapophysial joint may be a source of pain in a substantial minority of patients, a “facet syndrome” was unable to be demonstrated clinically. The prevalence of chronic lumbar zygapophysial joint pain is as high as 15% among younger patients4 and as high as 40% among older patients.5


The radiographic approach to the performance of diagnostic blocks of the lumbar zygapophysial joint innervation was confirmed to be target specific. It was further refined by Dreyfuss, with defined target points and needle trajectories required to provide specific anesthetization of the zygapophysial joint.6 The volume of local anesthetic injected should be limited to 0.4 mL to 0.5 mL to maintain the diagnostic specificity of the injection.


The medial branch nerves are not named for the transverse process they cross but rather for their originating somatic nerves. Each zygapophysial joint is innervated by two medial branches of the dorsal rami; at joints L1-L2 through L4-L5, both medial branch nerves must be anesthetized to achieve a diagnostic block. At the L5-S1 joint, the L4 medial branch and the L5 dorsal ramus must be anesthetized to achieve a diagnostic block. It is thought that lumbar medial branch blocks provide superior diagnostic specificity as compared with lumbar intraarticular zygapophysial injections. With intraarticular injections, if there is medial joint capsule incompetence, epidural extravasation may occur.


With this technique, the oblique view is the trajectory view, and needle placement is confirmed in the anteroposterior view. This oblique (trajectory) view is one of the multiplanar views that is used to guide needle placement.



Reporting of Diagnostic Results


Diagnostic accuracy is dependent on the reliable evaluation of the patient’s response to the block. The “double-block” protocol (as described in the International Spine Intervention Society Guidelines1) is not universal, and it has been challenged on the basis of both its cost effectiveness7 and the consideration that the radiofrequency neurotomy procedure carries no greater risk of complications as compared with the diagnostic block.9 The percentage of postblock improvement above which a patient may be considered to be a candidate for radiofrequency denervation (i.e., 50% versus 80%) has been studied, and it has been concluded that the optimal threshold cannot be determined.9



image Trajectory View




image Confirm the level (with the anteroposterior view).


image Tilt the fluoroscope’s image intensifier to line up the vertebral superior endplate and the inferior endplate at the appropriate orientation.


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


image For the L1 through L4 medial branches, the target needle destination is at the junction of the superior articular process and the transverse process, where the target nerve crosses midway between the superior border of the transverse process and the mamilloaccessory notch. This is often described as the level of the “eye of the Scotty dog.”


image For the dorsal ramus of L5, 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 that is similar to the lumbar medial branches at L1 through L4. The 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 the junction of the superior articular process and the sacral ala.


image Note that, for each lumbar zygapophysial joint, both of the nerves that innervate the joint will need to be anesthetized.

Related posts:

Atlantoaxial Joint Intraarticular Injection Lumbar Zygapophysial Joint Nerve (Medial Branch) Radiofrequency Neurotomy, Posterior Approach Thoracic Zygapophysial Joint Intraarticular Injection, Posterior Approach Thoracic Zygapophysial Joint Nerve (Medial Branch) Radiofrequency Neurotomy, Posterior Approach Thoracic Interlaminar Epidural Steroid Injection, Paramedian Approach Cervical Discography/Disc Access

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Dec 23, 2015 | Posted by in INTERVENTIONAL RADIOLOGY | Comments Off on Lumbar Zygapophysial Joint Nerve (Medial Branch) Injection, Oblique Approach

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