The medical branch block is both a therapeutic and diagnostic procedure that identifies pain in the facet joints. The facet joints are located on the rear of the spine at each vertebrae and are surrounded by small nerves called medial branch nerves that carry signals to and from the facet joints.
The physician uses live x-ray imaging called fluroscopic x-ray (contrast dye) and/or ultrasound to guide the needle into position and confirm the correct positioning of the needle. The anesthetic medication is then injected around the medial branch nerves temporarily blocking pain sensation.
The anesthetic injected during this procedure tests for pain relief. If pain relief is experienced then a longer lasting anesthetic is injected if not then the physician may test other, nearby, facet joint to determine the correct joint.