Diagnostic medial branch blocks

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Diagnostic medial branch blocks

Medial branch blocks involve injections to determine whether a patient is a candidate for radiofrequency facet ablation (rhizotomy).

The articular facets are small joints located on each side of the posterior spinal region.


The facet joints may be responsible for pain at every level of the spinal column. The posterior medial branch innervates the facet joint. A posterior medial branch block helps temporarily relieve pain the nerve is signalling to the brain. This test requires two or three separate injections.



After each step of the test, the patient completes a pain assessment form, which will be analyzed by the physician. If every step is conclusive, in theory the patient will become a candidate for radiofrequency ablation.



The physician uses fluoroscopy (radiography) to identify the posterior medial branch. After disinfecting the skin and applying anesthesia if necessary, he ensures the needle is properly positioned in the nerve region by injecting a small dose of contrast agent then taking an X-ray. Then, an anesthetic solution is injected. Following the procedure, the patient returns to the recovery room for about 20 minutes to confirm there is no allergic reaction to the injected substances.


Side effects:

Pain may increase during a few hours following the injection. Applying ice and taking an analgesic help to relieve pain.


Complications :

Complications are essentially related to the injection, the anatomy involved and the substances injected. Using radiography to confirm the injection’s pathway enhances the safety of the procedure. The risks of complications, such as infection or hemorrhaging, are the same as for any other type of injection, and are quite rare.



Fluoroscopy-guided injections are contraindicated during pregnancy. Report all allergies to medications or contrast agents to the physician.