Medial Branch Radiofrequency Ablation
As discussed in the text on Z-joint injections, the posterior section of the spine accounts for about 20-25% of low back pain and 54% of chronic neck pain. Pain from these structures is frequently a result of repeated bending, a hyper-extension (bending back to far) injury such as "whiplash", or through "wear and tear" of the facet joints, a problem which can happen with age.
While the providers at Ahwatukee Sports & Spine will often use Z-joint injections (in conjunction with physical therapy) as a diagnostic and potentially therapeutic treatment, on occasion pain will return because of substantial joint damage.
In these occasions, they may recommend ablation of the nerves innervating the involved joints. The Z- joint capsule (a ligament which surrounds the joint, keeping it together), cartilage, and facet bone are all innervated from nerves arising from the medial branches of the dorsal rami. Pain arising from these structures is transmitted through this medial branch innervation.
Medial branch blocks
If you have previously obtained relief from Z-joint injections, but the pain returned, or if the physician is trying to determine that pain is coming from the Z-joints, medial branch blocks will be recommended as a purely diagnostic procedure. During this procedure, a small amount of local anesthetic is placed on the nerves innervating the suspected joint(s) causing pain (each Z-joint is innervated by two medial branch nerves). Following the procedure, you pain is assessed and you are given a pain diary. Resolution of the pain you had before the procedure is considered confirmation that the pain is coming from the Z-joints. Insurance companies usually require two diagnostic procedures (medial branch blocks or Z-joint injections) before a radiofrequency neurotomy is approved.
What is radiofrequency ablation?
Radiofrequency ablation is a procedure in which a special needle is directed to a spot adjacent to the medial branch nerve. The needle is then connected to a radiofrequency generator which, as the name implies, produces a high-frequency radio wave. This wave produces a small area of heat in the tissue surrounding the needle (the nerve). This heated area is essentially burned, killing or ablating the nerve at that point. This ablation prevents pain impulses from traveling up the nerve to the spinal cord and brain, eliminating the perception of pain. The results of this procedure frequently last from 6 months to 2 years, though can be permanent.
How are these injections administered?
Certain medications may increase the risk of complications. If you are taking aspirin you should stop it 5 days prior to the procedure. If you are on Coumadin (warfarin), heparin, Lovenox, Ticlid (ticlopidine), Plavix (clopidogrel), or other blood thinning agents such as anti-inflammatory agents, please let your physician know at least one week prior to the procedure. You can continue to use Celebrex (celecoxib), Vioxx (roficoxib), or Bextra (Valdecoxib) before the procedure. Do not take your regular pain medications for six hours before or after the procedure. You should continue to take your routine medications (such as high blood pressure and diabetes medications) before the procedure. If you are on antibiotics please notify your physician, he may wait to do the procedure. If you have an active infection or fever we will not do the procedure.
For radiofrequency neurotomy, you should not eat or drink anything (except your routine medications) for the three hours prior to the procedure. For medial branch blocks and Z-joint injections it is routinely acceptable to eat and drink prior to the procedure as we do not frequently administer general anesthetic. You are expected to have a ride to and from the procedure. The procedure usually takes about one-half hour though you may be at the facility for as long as one and a half hours. For radiofrequency neurotomy an IV will be placed in your arm when you arrive at the facility. After this has been done and the doctor is ready, you will be taken to the room and positioned on the table.
Local anesthetic will be injected into the skin and underlying tissues to decrease the discomfort of introducing the spinal needle. Once the local anesthetic is working the spinal needle is advanced to the appropriate location using bones as landmarks. Your physician will use fluoroscopy (a live x-ray) and other technical aids to ensure that the needle is in the right place.
For medial branch blocks, the physician will place then needle adjacent to the nerve based on bony landmarks that can be visualized with the fluoroscopy unit. He will then inject a small amount of contrast to confirm that the needle tip is not in a blood vessel. If the needle is in the appropriate position, he will inject a small amount of solution to "block" the nerve. You will be expected to keep a pain diary following the procedure to record pain each hour and note how long the block lasts. Remember, this is a diagnostic test and not a permanent treatment for pain.
For radiofrequency ablation, the physician will place then needle adjacent to the nerve based on bony landmarks that can be visualized with the fluoroscopy unit (the same location used in medial branch blocks). He will place multiple needles based on how many nerves he plans to block. Once the needles are placed, he will connect the needle to the radiofrequency generator. You will be asked to let the physician know as soon as you feel a change in the quality or type of pain. This technique is used to localize the nerve and confirm the needle tip is very close to the nerve. The physician will then use another setting to stimulate a motor response which will make a small muscle in your back fire intermittently. The physician will closely watch your leg or arm to confirm that the needle is not near the spinal nerve. Once the doctor has adequately confirmed placement, he will inject a small amount of local anesthetic to deaden so there is no pain when the needle tip is heated. The physician will then reconnect the needle to the generator and ablate the nerve. It takes approximately 90 seconds to ablate each nerve. He will repeat this process for each nerve to be ablated. Your physician may inject steroid around the nerve after the injection to reduce inflammation after the burn, this may help to reduce discomfort after the procedure. It can take up to 3-4 weeks to notice the results following radiofrequency ablation.
What are the risks of these procedures?
With any operation or injection procedure there are risks. In the case of these procedures, the risks are small. These procedures are performed on the posterior spine and are thus away from the neuroaxis (spinal cord, etc). This dramatically reduces the risk of serious problems.
With medial branch blocks there are no specific side-effects or complications, only the general ones listed below.
With radiofrequency ablation, there are inherently more risks because your physician is creating permanent tissue damage. It is theoretically possible to have the needle too close to the spinal nerve. If the probe ablated the spinal nerve could result in weakness and numbness in the arm or leg. If at any point during the procedure you feel pain shooting into your arm or leg, please notify the doctor. This is a very rare complication and can usually be avoided with proper technique. Also on very rare occasions, the nerve that has been burned responds poorly to the procedure, becomes inflamed (neuritis) and produces increased pain. As mentioned above, your physician may inject corticosteroid following the ablation to help reduce the risk of this.
If you are allergic to one of the additives in the steroid solution you may experience a hot flush or develop a rash. However, this should get better within a few hours or days.
As with any injection through the skin, it is possible for bacteria to gain entry causing an infection. Your physician will use sterile technique and the risk of infection with these procedures is very small.
Sometimes a patient's blood pressure falls at the time of the injection. If so, the doctor will use the venous canula inserted before the epidural procedure commenced so that intravenous fluids or medication, if necessary, can rapidly control the blood pressure.
Some side-effects may occur as a result of the corticosteroid administered. If you have diabetes, you may notice that your blood sugars are elevated for 2-3 days following the procedure. If they are, usually only monitoring is required. However, if you are concerned, call your physician. Corticosteroids may also cause fluid retention, weight gain, alterations in skin pigmentation at the site of injection, fluid and electrolyte alterations and/or gastrointestinal upset. These side-effects are usually not serious.
How long does it take?
These procedures take 20 minutes to one hour depending on the number of levels involved. On occasion radiofrequency ablation can take longer if the nerves are difficult to localize. The patient will usually be in the recovery room for 15-30 minutes to one hour after the procedure.
Any of these procedures may be repeated. Medial branch blocks may be repeated with a different local anesthetic to absolutely confirm that blocking the medial branch nerves will be effective. Repeating this procedure is at the doctor's discretion.
Radiofrequency ablation may be repeated after 6 months should the pain return, though on occasion is permanent and does not need to be repeated.