Here's a dilemma neurosurgeons and orthopedic surgeons face when it comes to advising patients with chronic low back and leg pain from disc disease. Epidural injections are a common way to treat this painful problem. For more information on the treatment of chronic low back pain with epidural (steroid) injections, see A Patient's Guide to Epidural Steroid Injection.
Evidence is lacking in how well these injections work. The best way deliver the injections is also debated. With anywhere from 18 to 90 per cent effectiveness reported, it's difficult to assure patients that this treatment will work.
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.
The epidural space is normally filled with fat and blood vessels. Fluid such as the lidocaine and cortisone that can be injected is free to flow up and down the spine and inside the epidural space to coat the nerves that run inside the spinal canal.
Epidural injections are commonly used to control back and leg pain from many different causes. 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.
Some of the uncertainty in how well injections work for lumbar disc herniations is due to the fact that there are two different types of injections and three locations to give them. The injection solution can be a local anesthetic like lidocaine or bupivacaine. Or it could be one of those two numbing agents combined with a steroid (antiinflammatory medication).
There are several openings in the bones that surround the epidural space where a needle can be placed. The injection can be performed by placing the needle in one of three of these openings (caudal, interlaminar, transforaminal).
Each of these three types of ESI injections has advantages. But here is another dilemma in doing research studies to provide physicians with the evidence needed to support one approach over another. We don't have randomized, controlled, double-blind trials to compare patient results when using different types and locations of injections. That's where this study comes in.
The authors randomly divided a group of 120 adults with painful back and leg symptoms from lumbar disc herniation into two groups. Everyone in the study received at least one injection under fluoroscopic (real-time X-ray) guidance. All injections were given into the caudal opening.
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.
The first group received a caudal injection of just an analgesic compound (numbing agent for pain relief). The second group received an injection of a solution that contained a mixture of an analgesic agent (lidocaine) and an antiinflammatory (steroid). A second or third injection was given only if there wasn't enough pain relief or the pain came back. Patients could come back for additional injections for up to one year from the start of the study.
The patients did not know which group they were in. The physician who performed all of the injections didn't know what type of injection was being given. That's what makes this a double-blind (more objective) study. Results were measured on the basis of before and after pain levels, function, ability to go back to work, and use of oral pain relievers.
A successful result was considered pain relief with only one or two injections that lasted at least three weeks. It turns out that the steroid injection group had better overall results. They had more pain relief with the first injection than the other group. The pain relief lasted longer for the steroid group. And the steroid group had fewer injections during the year of this study.
The authors concluded that steroid epidural injections (more commonly known as epidural steroid injections or ESI) are superior to analgesic injections. This study only looked at patients with pain from disc herniations not any of the many other spinal problems injections are used for. And only caudal injections were used so there's still a need for further studies to evaluate (and compare) results among all three injection sites.
For patients who do not want steroid injections, injection of a local anesthetic can yield good results, too. They should be told that the results may not last as long as with steroid injection and that more injections may be required. Even so, epidural injection of an anesthetic is an acceptable treatment approach.
Reference: Laxmaiah Manchikanti, MD, et al. A Randomized, Controlled, Double-Blind Trial of Fluoroscopic Caudal Epidural Injections in the Treatment of Lumbar Disc Herniation and Radiculitis. In Spine. November 1, 2011. Vol. 36. No. 23. Pp. 1897-1905.