Epidural steroid injections (ESI) is one approach to the chronic low back and leg pain experienced by many patients. These injections control pain by reducing inflammation and swelling. They do not cure any of the diseases they are commonly used for, but can control the symptoms for prolonged periods of time. In some cases, the reduced pain makes it possible for the patient to participate in a physical therapy program, become more active, and be better able to control the symptoms with a conservative program.
When doing an epidural injection, the doctor inserts a needle through the skin so that the tip of the needle is in the epidural space. This space is the area between the bony ring of the spine and the covering of the spine called the dura. The dura is the sac that encloses the spinal fluid and nerves of the spine.
There are several openings in the bones that surround the epidural space where a needle can be placed. An ESI can be performed by placing the needle in one of these three openings. The three opening sites are caudal, interlaminar, and transforaminal. Each of these three types of ESI injections has advantages.
The caudal injection is performed at the very lower end of the spine through a small opening in the bones of the sacrum. The sacrum is made up of several vertebrae that fuse together during development to form a single large bone. This bone is where the pelvis connects to the spine. The opening at the tip of the sacrum leads directly to the epidural space. Fluid injected through this opening can flow upward through the epidural space to coat the nerves throughout the lower lumbar spine.
An interlaminar injection is performed by placing the needle directly in from the back of the spine between the lamina of two adjacent vertebra. The laminae (plural) form the outer rim of the bony ring of the vertebra. This places the tip of the needle in the back side of the spine. The advantage to this type of injection is that it is easy to do, even without the guidance of a fluoroscopic x-ray machine. The injection is usually done between the two vertebra that are most likely causing your pain. This puts the medications as close as possible to the problem. The disadvantage to this type of injection is that injected medication may stay in the back side of the spine away from the intervertebral disc.
A transforaminal injection is a newer type of injection that is done from the side of the spine, through the neural foramen. The neural foramen is the opening where the nerve root exits the spine.
There are two neural foramen between each vertebrae, one on each side. The doctor places the tip of the needle into the neural foramen using the fluoroscopic x-ray machine to watch and guide the needle into the correct position. The advantage to this type of injection is that it places the medication in the front of the spinal canal, near the intervertebral disc. The disadvantage is that this type of injection requires using the fluoroscopic x-ray to guide the needle placement.
Your doctor is recommending an ESI to try and reduce your pain. The ESI may also reduce numbness and weakness. With this information in mind, you can ask your surgeon which approach he or she is planning to do and perhaps more about why this method is best for you.
You should know that these injections are often temporary. Pain relief may last from a couple of weeks to a couple of months. They may be used to reduce your symptoms so that you can more easily begin a physical therapy program with less pain. They may also be used to reduce symptoms and let the body repair the underlying condition. This is something else you may want to discuss with your surgeon before the procedure.