What are Facet Blocks and Rhizotomies?
Facet blocks and rhizotomies are treatment options for back pain. Facets can cause neck or lower back pain. In the neck, facets can cause up to 30% of global neck pain and in the lumbar spine, it is less than 10%. Facet pain occurs typically with extension (bending backwards) but can cause pain with flexion also. Clicking or popping is typically caused by the facet but normally, the noise is not related to pain or dysfunction.
Diagnosis of facet pain is relatively simple and related to the “facet block”. This injection into the facet contains two medications, a numbing agent like novacaine and a corticosteroid. Whether you know it or not, you have had a diagnostic type numbing injection before. When you go to the dentist, you have had an injection into the jaw to numb the area that the dentist is going to work on. He is blocking the sensory nerve to the jaw. This is the exact same experience you should have with an injection into an area of the spine in question.
How Does a Facet Block Work?
The facet is populated by pain nerves (nociceptors) and can cause pain. The purpose of the diagnostic pain injection is to temporarily anesthetize (numb) the potential facet pain to prove it is the pain generator. Just like in the jaw, the numbing sensation lasts for 2-3 hours.
After the injection, you must get up and test the blocked facet or facets. If the surgery center keeps you sedated or in bed for the 3 hours after the injection, the diagnostic portion of the block is lost along with the important information that goes along with the block. You must get up and repeat the activity that causes the pain in the next 3 hours as well as keep a record (a pain diary) of the response to the activity. If walking a mile causes onset of pain, then by all means, walk. If prolonged sitting or bending or neck extension causes pain-do those maneuvers and keep a record of the pain! A pain diary is essential to record the responses.
How to Know if a Facet Block Worked?
If the block gives good pain relief, then the facet is most likely causing some or most of the pain. There is a caveat. The injection is typically placed into the capsule of the facet and the capsule may have a tear in it. If this tear leaks anesthetic onto the disc and nerve root underneath the facet, these structures will also be “numbed”. If the pain has originated from either lower structure, this results in a false positive test (a test that falsely indicates the facet being tested is the painful one).
There is another way to test the facet. The nerve supply to the facet comes from medial branches of the recurrent nerve of the spine. Instead of blocking the facet itself through the capsule, you can block these medial branches (medial branch blocks). They have a relatively consistent location along the back of the vertebra. The effect will be the same as standard facet blocks- numbness of the facet and hopefully- pain relief.
Some physicians perform the facet block at one appointment and the medial branch block at the next appointment to confirm the findings.
The steroid can give long term relief of the facet pain and may be the only treatment needed for this pain. Injections can be repeated intermittently.
What is a Rhizotomy?
There is an outpatient procedure to interrupt the nerves that transmit the facet pain. This procedure is called a dorsal root or medial branch rhizotomy. In this technique, a needle is place into the spine right on top of the medial branch of the nerve that feeds the facet. Using electrical current, the needle tip heats up-destroying the nerve and commonly, stopping the pain transmission. There are normally two nerves that feed a facet so for one facet, two ablations are needed.
This procedure works for both the neck and the lower back if the facet is causing a large percentage of the pain. There is some evidence that this may also work for sacroiliac pain. It must be stated that most sacroiliac pain is NOT from the sacroiliac joint.
For more information on facet blocks and rhizotomies, or for additional resources on treatment options for pain relating to the neck, back or spine, please contact Dr. Donald Corenman, Colorado spine surgeon, at 970-479-5895.