The facet joint block is both a test and a type of treatment. A local anesthetic medication-such as lidocaine or Novocain-is injected into the facet joint or the small nerve branches going to the facet joint. This same type of medication is used by a dentist to numb your jaw or by a doctor to sew up a laceration. The lidocaine numbs the area around the facet joint. If your pain goes away, the doctor can assume that the facet joint is contributing to the problem.
Like other joints in the body, facet joints can cause pain if they are irritated or inflamed. The facet joint block is used in what is called a "therapeutic trial." This means that when the test is done, it should relieve your symptoms if the problem is from the structure being treated. For example, medication injected into the joint during a facet joint block should numb the spot and take pain away. Cortisone is sometimes used with the anesthetic to decrease inflammation in the joint and give relief for several weeks or months. The relief is usually temporary.
You will probably be given medication to help you relax, along with a local anesthetic around the area of the back where the test will be performed. A long needle is inserted into the center of the facet joint or next to the small nerve branches that go to the joint. The needle is inserted from the back. The doctor watches on a fluoroscope as the needle is inserted to make sure it goes to the right spot. The fluoroscope is a special X-ray TV that allows the doctor to see your spine and the needle as it moves. Once the needle is in the facet joint or next to the nerve branch, a combination of anesthetic and cortisone is injected.
A facet joint block only shows how your symptoms react to the injection. It does not involve taking any pictures, except to make sure the needle is placed in the right spot. It does not give specific information about the nerves or discs.
This test has more risks associated with it than most. A facet joint block requires a needle to be inserted into the back. The risks include infection of the joint and an allergic reaction to the medication that is injected. Doctors generally prefer to use "noninvasive" tests first, such as the MRI and CT scan. These tests, along with facet blocks, help doctors clarify the diagnosis and choose the best way to treat the problem.