FACT SHEETS
Medial Branch Blocks
Medial branch blocks are diagnostic and/or therapeutic procedures for facet joint pain. The procedure consists of injecting local anesthetic into the joint or the nerves that supply it.
If the patient experiences significant pain relief while the anesthetic is active, this suggests the facet joint is the pain generator.
This injection procedure is referred to as a "block" because its purpose is to interrupt and test for whether the targeted injection in that area will result in "blocking" the pain signals for longer-term treatments.
Should a medial branch block provide significant pain relief, subsequent treatments are then normally conducted, such as radiofrequency ablation where the nerve is not just anaethestised and instead burned for a longer-term, long-lasting deadening of the pain.
THE DIAGNOSIS OF FACET JOINT PAIN
Facet joint pain commonly manifests as low back pain with or without referred pain radiating into the leg. Damage to facet joints can occur during accidents such as car crashes, and these injuries may not be visible on imaging studies including X-rays, CT scans, or MRI scans.
To determine if a facet joint is the source of pain, we inject local anesthetic into either the joint itself or its nerve supply. We can target both the joint and its nerve supply because the facet joint connects to the spinal cord through medial branches of the adjacent dorsal rami—this is why these injections are called medial branch blocks.
Research indicates that a single successful block suggests a 70% probability that facet joint pain is the correct diagnosis. This means misdiagnoses can occur. Performing a second positive block increases diagnostic certainty to 90%.
For persistent chronic pain requiring specific facet joint treatment, medial branch blocks can be used prior to radio-frequency neurotomy (RFN) or radio-frequency denervation. This procedure involves creating heat lesions on the nerve and can provide extended pain relief.
INJECTION PROTOCOL
The primary purpose of the injection is to evaluate whether pain levels change during the 6 hours following the procedure. Consequently, implementing a consistent pain measurement method is essential. The Visual Analog Scale (VAS) is commonly used, rating pain from 0 to 10—where 0 represents no pain and 10 indicates extreme pain that completely inhibits thinking, movement, and normal functioning.
Patients should refrain from taking any pain medication on the day of injection to ensure an accurate assessment of pain changes. For the procedure to be properly evaluated, the patient's pain should register at least 4/10 on the VAS scale on the injection day.
THE PROCEDURE
The injection requires inserting a needle through the skin under X-ray guidance. The needle is positioned directly against the bone and is similar in thickness to acupuncture needles. Typically, only 1-2 facet joint levels are tested during a single session to ensure the diagnosis identifies specific problem areas in the lumbar spine.
It's perfectly normal to feel anxious about the procedure. However, you can be reassured that these injections are very safe, generally involve minimal pain, and can be completed quickly.