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).

Watch: Epidural Steroid Injections for Back Pain and Leg Pain Video

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.

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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.
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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.