In discussing common spinal injections, it's important to remember what we’re trying to achieve and then choose the appropriate tool for the job. So, to discuss the injections, we'll break them up into small categories.
Epidural steroid injections can be done in mainly two ways. Now, first of all, what we're trying to achieve is we’re trying to place the steroid into the epidural space. Epidural space in itself denotes space that is intimately located above the dura. Dura is the outermost layer covering the spinal cord and the nerves that exit the spinal cord. Most of the inflammation occurs in that area and that is the area that we can place the medications most safely. This can be approached in two ways. One is what’s called "interlaminar" - that means between these lamina. That can be approached from what's called paramedian - or just off the mid-line - approaching this way. Another approach is called the transforaminal - what that means is "across the foramen." Foramen being this opening through which the nerve exits. The approach is taken by going into - into a space where the nerve usually doesn't appear and this is done under the guidance of x-ray or fluoroscopy.
Another type of injection is called selective nerve root block. Selective nerve root block is selectively choosing a specific nerve in order to determine whether that nerve is causing the pain. And in order to do that, we approach under the guidance of fluoroscopy, to target a specific nerve then place a small amount of (usually) contrast to outline that we are really concentrating on this nerve root, and then place a very small amount of anesthetic. Now, the small amount is important because we don't want that anesthetic to spread anywhere else and affect our outcome. If the pain is relieved with this injection, then we know that was the cause of the pain or a pain generator.
Another injection is a facet joint injection. This can be approached in two ways. One is the injection into the joint itself and in order to do that we use fluoroscopy for guidance and we approach the joint itself, going into the joint, and then placing the medication into the joint. And the reason to do that is for one to determine if injecting anesthetic and corticosteroid will relieve the pain - and that is the diagnostic part of this - corticosteroid in turn reduces the inflammation.
Another way to approach facet mediated pain is by blocking the nerve that actually transmits the information or transmits that pain. And the reason we can do that is because, anatomically, it is consistently found in the same place. It is found traveling along this path. And what we can do, is once again under fluoroscopic guidance, we approach the anatomical location of this branch placing a small amount of medication, blocking the transmission of that nerve temporarily. And that, once again, diagnostically tells us: if we block this nerve, does this relieve the pain? Now, it’s not as simple as that because there are two nerves that usually supply each facet joint, so in order to really effectively block one joint, we have to block two nerves and that way we know that that joint is blocked and then we see if it truly alleviates the pain or not.
That leads me into another type of an injection, which truly is not an injection, but more of an intervention to treat facet joint pain - that is the medial branch rhizotomy. And in order to do that, what we do is we place a probe - that is just like a needle - along the path of this medial branch and then we use radiofrequency energy to concentrate at the tip of that probe to heat it up and then lyse the little nerve that travels along the path, effectively eliminating the transmission of the pain. The effect of this doesn't happen right away; it takes several weeks to take effect, but it provides a longer-term relief for people suffering from facet mediated pain.
Another type of a spinal injection is used to treat and diagnose sacroiliac joint pain. So, once again under fluoroscopic guidance in order to ensure the safety as well as precision, we go into the sacroiliac joint placing a small amount of contrast to outline where the medication is going to spread, then we use a small amount of anesthetic with corticosteroid. The anesthetic serves as the diagnostic portion - if the pain is eliminated, then we know that was the pain generator and we've effectively diagnosed sacroiliac joint pain. Then, corticosteroid reduces the inflammation that usually is the cause of the pain and that is the therapeutic portion of this.
There are many other interventions that we can use for the spine, but these are the more common ones.
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