How does burning nerves help my back pain?
If you have mechanical lower back pain, you may be a candidate for a procedure called Radiofrequency Ablation (RFA).
There are a number of potential causes for lower back pain. If you have pain that is either on one or both sides your lower back, without radiation into the legs, there is a chance that the source of your pain is from the posterior joints of the spine called the facet joints. Each bone of the spine, called a vertebral body, sends a posterior projection up and down. Where each of these projections meet the adjacent segment above and below, a joint is formed. This joint allows us to flex forward, bend backwards, and twist side to side. The joint is a synovial joint, like other synovial joints in our body such as the shoulder and hip. It is a very small joint, but it is often a source of pain in the lumbar spine. The joint gives what we call a referred pattern of pain that is often more diffuse than just pain at the level of the joint itself. The joint can look normal on Xray, CT, or MRI and still cause pain, especially if it is injured in an acceleration/deceleration incidents. There are clues on a physical exam that this is the source of your pain, but this is not always definitive.
The sensory input from these joints to the brain is well understood. There are small nerves called Medial Branch Nerves (MBNs) that send a signal of pain from these joints. Each joint has 2-3 nerves that carry most of the sensation from the joint. The anatomic location of these sensory nerves is well known as well. We can find out if your pain is from a facet joint by numbing the nerves and assessing afterwards if your back pain is decreased or not. This diagnostic procedure is simple and quick. You do not need sedation. It must be done under x-ray guidance though. A very small needle is placed next to the nerve and a very small amount of local anesthetic is injected to make sure we anesthetize that nerve and only that nerve. This is usually entails three MBN blocks on either side of your back, depending on the distribution of your pain. If you have greater than 50% relief of your pain after the procedure, we consider that a positive diagnostic response. This relief does not usually last long though. If you have a positive diagnostic response, you will then be scheduled a second procedure that we term confirmatory MBN blocks. It is completed similarly to the diagnostic injection, but often different strengths of local anesthetic are used to confirm that the results from the diagnostic injection was not what we call a placebo response. If your pain is again decreased after the confirmatory MBN block, then you have a diagnosis of facet mediated pain.
There are times when patients will get prolonged relief from the injections alone. Other times, the injections are positive but not long lasting. If you have had positive diagnostic and confirmatory MBN blocks, then that is an excellent prognostic indicator that you will have good response from the procedure mentioned above, Radiofrequency Ablation. This procedure is a little more involved, but it should not be painful for you. Again, you do not need sedation. Local anesthetic is sufficient to make it a comfortable procedure for you. If you are nervous, an oral sedative can be given for you to take before though.
The RFA needle is an insulated needle with a curved open tip. There are different sizes we use, depending on which nerves are being denervated. The RFA needle is placed, under Xray, to have the tip lie parallel to the MBN that was anesthetized in the previous diagnostic injections. A sensory test is done to assure that it is placed close to the nerve. Then a motor test is done to assure that the needle is not close to the motor nerve that travels into your leg. Once it is assured that the needle is placed in an accurate and safe location, more local anesthetic is administered. Then the actual RFA procedure is done, which takes only a few minutes. Utilizing radiofrequency energy, heat is generated at the open tip of the RFA needle, adjusted to a temperature we can control and for a length of time we can control, creating an ellipse of cauterization at the tip of the needle. You should not have pain during the heating procedure, but you can feel a pressure or warmth in the lower back. This heat does not destroy the nerve, but it denervates the nerve sheath enough that you should have 6-12 months of relief of your pain before the MBN regenerates. If you have positive diagnostic and confirmatory MBN blocks, there is an 80% chance that RFA will be able to help your pain. You are eligible for repeat RFA in the future if needed. No steroids are used in this procedure. It is a simple and safe procedure for treating facet mediated pain.