A to Z of Therapies
Injection Therapy
January 19th, 2009
Using injections for back pain relief
Injections comprise another relatively conservative treatment option for low back pain. They are typically considered as an option to treat low back pain after a course of medications and/or physical therapy is completed, but before surgery is considered. Injections can be useful both for providing pain relief and as a diagnostic tool to help identify the source of the patient's back pain.
How injections relieve back pain
For pain relief, injections can be more effective than an oral medication because they deliver medication directly to the anatomic location that is generating the pain. Typically, a steroid medication is injected to deliver a powerful anti-inflammatory solution directly to the area that is the source of pain. Depending on the type of injection, some forms of low back pain relief may be long lasting and some may be only temporary.
Injections to diagnose causes of back pain
Diagnostically, injections can be used to help determine which structure in the back is generating pain. If lidocaine or similar numbing medication is used, and the patient feels temporary relief after an anatomic region is injected (e.g. facet joint or sacroiliac joint), it can then be inferred that the specific region is the source of the pain. When considered in conjunction with a patient's history, physical exam, and imaging studies, injections used for diagnostic purposes can be very helpful in guiding further treatment for the patient.
Different kinds of injections for pain relief include:
a) Epidural Steroid injections
How an epidural steroid injection works
The most commonly performed injection is an epidural steroid injection. In this approach, a steroid is injected directly around the dura, the sac around the nerve roots that contains cerebrospinal fluid (the fluid that the nerve roots are bathed in). Prior to the injection, the skin is anesthetized by using a small needle to numb the area in the low back (a local anesthetic).
Epidural injections help reduce inflammation
Injecting around the dura sac with steroid can markedly decrease inflammation associated with common conditions such as spinal stenosis, disc herniation or degenerative disc disease. It is thought that there is also a flushing effect from the injection that helps remove or "flush out" inflammatory proteins from around structures that may cause pain.
Epidural steroid injection success rates
An epidural steroid injection is generally successful in relieving lower back pain for approximately 50% of patients. While the effects of the injection tend to be temporary (one week to one year), an epidural can be very beneficial in providing relief for patients during an episode of severe back pain and allows patients to progress in their rehabilitation.
Frequency for epidural steroid injections
There is no definitive research to dictate the frequency of the epidural steroid injections; however, a limit of three injections per year is generally considered reasonable. There is also no general consensus in the medical community as to whether or not a series of three injections need always be performed. If one or two injections resolve the patient's low back pain, some physicians prefer to save the one or two additional injections for any potential recurrent low back pain.
Generally, there are few risks associated with epidural injections. The risks are remote and include:
- A wet tap may occur, which means that the needle has penetrated the dural sac into the cerebral spinal fluid (CSF). A wet tap may result in a CSF leak and a spinal headache.
- Infection into the epidural space is also a remote risk.
- While there is no risk of paralysis (since the spinal cord ends at a higher level in the spine), there is a remote risk of damage to a nerve root.
Patients who should avoid epidural injections
Epidural steroid injections should not be performed on patients whose pain is from a tumor or infection, and if suspected, an MRI scan should be done prior to the injection to rule out these conditions.
b) Selective nerve root block (SNRB) for diagnosis and back pain management
Another common injection, a selective nerve root block (SNRB), is primarily used to diagnose the specific source of nerve root pain and, secondarily, for therapeutic relief of low back pain and/or leg pain.
When a nerve root becomes compressed and inflamed, it can produce back and/or leg pain. Occasionally, an imaging study (e.g. MRI) may not clearly show which nerve is causing the pain and an SNRB injection is performed to assist in isolating the source of pain. In addition to its diagnostic function, this type of injection for pain management can also be used as a treatment for a far lateral disc herniation (a disc that ruptures outside the spinal canal).
In an SNRB, the nerve is approached at the level where it exits the foramen (the hole between the vertebral bodies). The injection is done both with a steroid (an anti-inflammatory medication) and lidocaine (a numbing agent). Flouroscopy (live x-ray) is used to ensure the medication is delivered to the correct location. If the patient's pain goes away after the injection, it can be inferred that the back pain generator is the specific nerve root that has just been injected. Following the injection, the steroid also helps reduce inflammation around the nerve root.
Success rates vary depending on the primary diagnosis and whether or not the injections are being used primarily for diagnosis. While there is no definitive research to dictate the frequency of SNRB's, it is generally considered reasonable to limit SNRB's to three times per year.
Technically, SNRB injections are more difficult to perform than epidural steroid injections and should be performed by experienced physicians. Since the injection is outside the spine, there is no risk of a wet tap (cerebrospinal fluid leak). However, since the injection is right next to the nerve root, sometimes an SNRB will temporarily worsen the patient's leg pain.
c) Facet joint block for back pain management
In cases where the facet joint itself is the pain generator, a facet block injection can be performed to alleviate the pain. Similar to SNRB's, facet block injections are a diagnostic tool used to isolate and confirm the specific source of back pain for the patient. Additionally, facet blocks have a therapeutic effect as they numb the source of pain and soothe the inflammation for the patient.
The facet joints are paired joints in the back that have opposing surfaces of cartilage (cushioning tissue between the bones) and a surrounding capsule. Twisting injuries can cause damage to one or both facet joints, and cartilage degeneration associated with aging may also cause pain.
In a facet block procedure, a physician uses fluoroscopy (live x-ray) to guide the needle into the facet joint capsule to inject lidocaine (a numbing agent) and/or a steroid (an anti-inflammatory medication). If the patient's pain goes away after the injection, it can be inferred that the pain generator is the specific facet joint capsule that has just been injected.
If the facet block procedure is effective in alleviating the patient's low back pain, it is often considered reasonable for the procedure to be done up to three times per year. There are very few risks associated with this technique.
d) Facet Rhizotomy injection
In some low back pain programs, if three facet block injections provide good but temporary relief of the patient's pain, a facet rhizotomy injection may be recommended. The purpose of a facet rhizotomy injection is to provide lasting low back pain relief by disabling the sensory nerve that goes to the facet joint.
In this injection procedure a needle with a probe is inserted just outside the joint. The probe is then heated with radio waves and applied to the sensory nerve to the joint in order to disable the nerve. Theoretically, by deadening the sensory nerve to the facet joint, a facet rhizotomy effectively prevents the pain signals from getting to the brain.
A facet rhizotomy injection is successful in providing lasting pain relief for approximately 50% of patients.
e) Sacroiliac joint block injection
Sacroiliac (SI) joint blocks are injections that are primarily used for diagnosing and treating the low back pain associated with sacroiliac joint dysfunction. The SI joint lies next to the spine and connects the sacrum (bottom of the spine) with the pelvis (hip).
In an SI joint block injection approach, a physician uses fluoroscopic guidance (live x-ray) and inserts a needle into the sacroiliac joint to inject lidocaine (a numbing agent) and a steroid (an anti-inflammatory medication). It takes a highly skilled and experienced physician to be able to insert a needle into the sacroiliac joint.
An SI joint block injection may be repeated up to three times per year. For the treatment to be successful, the injection should be followed by physical therapy and/or chiropractic manipulations to provide mobilization and range of motion exercises.
SOURCE: www.spine-health.com
A to Z of Therapies
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