Facet joints are small joints between the vertebrae in the back of the spine. Sometimes they can be a source of back pain. One way to determine whether or not they are causing pain is by performing a medial branch nerve block injection. If the temporary nerve block relieves pain, it's a good indicator that the facet joints are the source of pain.
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This close up view shows the back of the spine. You can see the blue disc between the vertebrae.
In this image, the facet joints,also called zygapophysial joints, are shown in purple. Located behind the spine, they add stability to the spine as it twists, flexes, and bends.
Medial branch nerves, shown here in purple, are located on each facet joint. They carry pain signals to the brain.
Conditions such as spinal stenosis and osteoarthritis, or an injury to the spine could all lead to inflammation of the facet joints. When inflammation occurs, the medial branch nerves transmit pain signals to the brain. If your physician suspects this is the source of your pain, they may recommend a medial branch nerve block injection to make the diagnosis.
How the injection works
Your doctor will ask you to lie down on a table. A local anesthetic will numb the skin and tissue around the facet joint.
Using X-ray guidance, called fluoroscopy, your physician will direct a small needle over the medial branch nerves. A small amount of contrast dye is injected to confirm that the medicine covers the medial branch nerve.
Once your physician determines the correct location of the nerve, he or she will slowly inject a numbing medicine, called an anesthetic, slowly onto each targeted nerve. Usually, two adjacent nerves will be targeted at the same time.
If you experience immediate and significant pain relief after the injection, you can pin- point the source of your pain to the facet joint, and you may be a candidate for a follow-up procedure, called a medial branch radiofrequency neurotomy, which may provide longer pain relief.