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There are two reasons to perform injections into the spinefor diagnosis and for treatment. Injections, often referred to as blocks, are called diagnostic injections when they help locate the source of the pain.
X-rays and scans are pictures of anatomy, not pictures of pain. It is the job of the doctor to decide if something that looks abnormal on X-ray is the source of the pain or just an incidental finding on scan. If the abnormality seen on scan is a source of pain, then anesthetizing the abnormality should make the pain better temporarily. If the pain improves, then the abnormality is contributing to the pain. If the pain does not improve, then the abnormality was not the source of the pain.
There are several types of diagnostic injections. These include selective nerve root injection, medial branch block (MBB), and sacro-iliac joint block, among others. The choice of injection is based on the patients history, examination, and findings on scan or X-ray.
Selective Nerve Root Injection is a procedure in which we numb up one of the major nerves that comes from the spine. It is much more useful for diagnosis than an epidural. If we think of an epidural as a shotgun, then a selective nerve root injection is using a rifle with a laser scope on it.
Medial Branch Block (MBB) is the procedure that is used to determine whether one or more facet joints is the source of neck or low back pain. There is very poor correlation between the X-ray or CT appearance of the joint and whether it hurts. Joints that look bad may not hurt, and joints that look normal may be painful. The medial branches are the nerves that supply the facet joints. If we anesthetize the nerves to a specific joint, the pain that goes away was coming from the joint. If we prove that the joint is the source of the pain, we can perform a neurotomy, (heat the nerve) which may keep the pain under control for six to eighteen months. If the pain is not relieved by MBB, then the facet joint is not the cause of the pain.
Sacro-iliac joint injection is used to see if the sacro-iliac joint is the cause of pain. Unfortunately research has proven that the physical examination, even by an expert, cannot tell if the joint is painful. If we anesthetize the sacro-iliac joint, any pain that goes away was coming from the joint. If we prove that the joint is the source of the pain, we can inject it with cortisone, and that often helps.
Discography (also called discogram) is perhaps the most controversial of the spinal injections. That is because in 1964, a research project suggested the test was not reliable, and many doctors think only of the 35 year old research and have not learned the newer research about this test. There have now been hundreds of newer studies, most of which find that discography is a very useful test. It is not a routine test. It is used in some patients when surgery is being considered. Discography can tell us whether a disc that looks abnormal on MRI scan is a cause of pain. When we inject a normal disc, it does not hurt. When we inject an abnormal disc it may hurt. If the injection is painful, and the pain resembles the pain the patient has on a day to day basis, this is a positive test. We look at the X-rays, but it is the pain response that is most important.
There are two reasons to perform injections into the spinefor diagnosis and for treatment. Injections, often referred to as blocks, are called therapeutic injections when they relieve pain for more than the duration of the local anesthetic.
There are many types of therapeutic injectionsepidural injection, medial branch neurotomy, facet joint injection, and sacro-iliac joint injection, among others. In most instances, a long-acting cortisone medication is placed in the spinal area that hurts. This may reduce the pain for weeks or even months, when it is successful. These injections never cure a spine problem, but they can relieve pain to some degree while either nature heals, or physical therapy helps a person control the pain.
Epidural injections are performed very often. They can relieve pain if it is due to inflammation in the spinal canal. They do not work for disc pain, facet joint pain, or other sources of pain. They are most effective for patients with an acute disc herniation or for spinal stenosis. They can be used safely three times per year.
Medial Branch Neurotomy is a procedure in which the nerve to the facet joint is heated. It can relieve the pain from a facet joint, when it is successful.
Facet joint injections are occasionally helpful, but not usually as effective as neurotomy.