Getting to the Source of Your Pain
The discomfort of low back pain can cause you to stop participating in activities you like or need to do each day. Your doctor may prescribe exercises, physical therapy, and a short course of medication to help relieve the pain. In certain cases, the doctor chooses to include spinal injections as part of nonoperative treatment. Spinal injections enable the doctor to diagnose the source of your low back pain or to reduce the pain.
What are they?
Spinal injection procedures involve injecting medications through a needle placed into a structure or space in the spine. Typical medications used include local anesthetics and corticosteroids. Local anesthetics numb the nerves and temporarily prevent them from sending pain signals to your brain. Corticosteroids help reduce local inflammation that may be irritating nerve fibers, thereby preventing the pain signals from being generated.
Several structures in the spine receive a nerve supply. When the structures are damaged or are not functioning correctly, their nerves send pain signals to the brain. The most common pain-generating structures include intervertebral discs (shock absorbers between back bones), facet joints (joints uniting back bones), nerve roots and dorsal root ganglia (collections of nerve cells near a nerve root), sacroiliac joints (joints uniting the hip and tail bones), spinal ligaments (tissue connecting back bones), and muscles. The doctor injects local anesthetics through needles placed in or around the structure that he or she thinks is causing the pain. If that structure is responsible for your pain, then the medication should give pain relief. Unfortunately, local anesthetics work only temporarily because your body breaks down this medication after a few hours. Therefore, corticosteroids usually are injected along with the local anesthetics to give longer relief.
What types of procedures are available?
Typical spinal injection procedures for the lumbar spine (lower back) include epidural steroid injections, facet joint or nerve blocks, sacroiliac joint injections, sympathetic ganglion blocks, and discography (Figs. 1 and 2). The doctor often uses an injection of colorless, iodine-based contrast and a special type of x-ray to help him or her place the needle in the correct location.
Epidural injections involve placing medications in the fatty space that surrounds the spinal sac and its nerve roots in an attempt to relieve back and leg pain. These injections are usually given to people with an intervertebral disc herniation (bulging of disc material into the spinal canal, putting pressure on a nerve) or spinal stenosis (narrowing of the space in the spinal canal through which nerves pass) and associated leg pain.
Injections into the facet joints or sacroiliac joints are used when your doctor suspects that one of these areas is the source of your low back or associated buttock, hip, or leg pain. For diagnostic purposes, small amounts of local anesthetic also may be applied to the nerves supplying these joints.
Lumbar sympathetic ganglion blocks involve placing a needle along the front of the spine and injecting local anesthetics on a collection of nerve cells (ganglia) in an attempt to determine the origin of your limb pain. The doctor usually chooses to use this block if you have widespread limb pain, swelling, and skin that is hypersensitive to touch.
Discography involves placing needles into the center of a disc and injecting an iodine-based contrast. This test is only used for diagnosis, and it enables the doctor to see if the disc is responsible for your low back and leg pain. Imaging tests (e.g., magnetic resonance imaging and computed tomography scans) may show disc abnormalities, but they cannot tell the doctor if that disc is responsible for your pain; discography is the only way to determine this. The doctor also can use discography when he or she is considering treating your condition with spinal fusion (permanently joining two or more back bones).
When are spinal injections used?
One or more of these procedures usually is considered if you have low back and leg pain that does not get better with other nonoperative treatments, such as oral medications (e.g., ibuprofen, a brief course of narcotics), exercises, mobilization (e.g., osteopathic treatments), physical therapy modalities (e.g., heat, ice, ultrasound, electric stimulation), or bracing. Usually, these people have moderate to severe pain that interferes with several daily activities and that has lasted longer than a few months. Many times, these injections can help speed up the body's own recovery process, thereby shortening the painful episode.
Who cannot have them?
In general, you cannot have one of these procedures if
The number of injections you will have usually depends on the type of spinal injection and whether it relieves your pain. In general, diagnostic injections (except discography) are performed twice. Therapeutic injections can be repeated if they provide long-term relief (i.e., several months or more). In practice, only one or two injections are usually administered, and, typically, you will not have more than three to five injections each year. If you do not have long-term relief, you may need a more permanent intervention such as surgery.
Spinal injections can be a useful addition to the nonoperative treatment of your low back and leg pain. By getting to the source of your pain, the injections may relieve your pain for weeks, months, or years.
Douglas T. Cannon, M.D.