Because the human body is quite redundant in overlap of nerves that network with each other in vast intercommunication in the spinal cord and brain, the origin of a painful body part can be confusing to both patients and physicians. For example, irritation of a nerve in the spine can be perceived as pain down the leg, and irritation of a spinal nerve in the neck can be perceived as pain in the arm, even though there is nothing wrong with the leg or the arm. Sometimes these referred pains can focus on a joint, and it is difficult to tell whether the joint is the source of the pain or if it is being referred from the spine. In these situations, sometimes injections are used to try to sort out the origin of the pain. Although not foolproof, when the patient has a prolonged period after an injection, it is suggestive that whatever area was injected is the likely culprit as far as being the source of the pain. In areas that commonly receive referrals from the spine, such as the sacroiliac joint, for instance, injection and the response to it is the most common way in which the diagnosis of pain from the sacroiliac joint is made.
In the spine, the spinal nerves lie in a sac filled with fluid called the dural sac. Around this sac and within the spinal tunnel where the nerves run is a space called the epidural space. This is probably the most common site where steroid injections are given for back and neck problems. To be accurately located, fluoroscopy is usually used to identify anatomically the site to be injected, and sometimes contrast agent, which is visible on fluoroscopy observation, is used to verify exactly where the medication is going within the spine. In addition to placing medication in the epidural space, it can also be placed on the points where nerves exit the spine, called neural foramina. These injections are called selective nerve root blocks. Another common area of spinal injections are the small joints in the back of the spine called facet joints. These finger-sized joints are complete joints with joint fluid and smooth joint surfaces, just like the joints in the finger, knees, or hips. Depending on a person’s symptoms and the findings on his diagnostic studies, the treating physician will decide which sort of injection is most likely to be successful. When problems are not too severe structurally, the injections may appear to cure the problem or may last for prolonged periods of time, such as over a year, even though the medication is dissipated in about six weeks. The injections can be especially effective in conjunction with proper body mechanics training and exercise programs that diminish the irritative stresses on the structures in the spine, so that when the medication is gone the problem does not recur.
The corticosteroid medication does have potential side effects. These are usually normal and of low consequence unless the medication is taken for prolonged periods of time. Usually, with more prolonged exposure to higher doses of corticosteroids, side effects can include abdominal fat accumulation, acne, moon face, plethora (redness in the face), unusual euphoria, depressed feelings, osteoporosis, and hip arthritis. Patients who are diabetic will usually have elevation of their blood sugar while being exposed to the corticosteroid hormone increase. For these reasons, in general we prefer to limit corticosteroid injections to three a year, but this, of course, is relative to the severity of the problem and usefulness of the injections on a case-by-case basis.
Radiofrequency Ablation Procedures (Rhizotomy)
In some case, typically when corticosteroid injections are effective but do not last, usually this involves the facet joints. The small nerves that carry pain signals to these joints can be cauterized without particular detriment. These procedures involve heat-generating devices that essentially destroy the small nerves and can sometimes be useful in inducing remissions in symptoms for six to twelve months or longer. Usually, before this procedure is considered, local anesthetics are given and degree of relief assessed. If this gives temporary excellent relief, then more permanent radiofrequency ablation procedures are considered. Since the nerves involved do not play any significant role in muscle function, the procedures are safe when done properly.
Spinal injections are commonly administered for spinal problems that are not responding to first-line conservative treatment, in situations where a great deal of discomfort is involved and rapid improvement in symptoms is needed, or in situations where surgery may or may not be required.
The most common medication injected is corticosteroid, which is a hormone that is normally secreted by the adrenal gland and is necessary for survival to some level. The corticosteroids are different than the anabolic steroids, such as testosterone, that have a muscle-building effect. Corticosteroids have a very strong anti-inflammatory effect, similar to but more powerful than ibuprofen and Naprosyn, which are non-steroidal anti-inflammatory medications taken orally. The corticosteroid injection preparations are designed to stay in the area of injection for up to six weeks. The medication can be placed in almost any area of the spine is commonly used in any other joint or area of local inflammation.
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