Epidural Steroid Injections
Efficacy of Injections
Although many studies document the short-term benefits of epidural steroid injections, the data on long-term effectiveness are less convincing. Indeed, the effectiveness of lumbar epidural steroid injections continues to be a topic of debate. This is accentuated by the lack of properly performed studies.
Injections for Pain Management
For example, many studies do not include use of fluoroscopy or x-ray to verify proper placement of the medication despite the fact that fluoroscopic guidance is routinely used today. Additionally, many studies do not classify patients according to diagnosis and tend to ‘lump’ different types sources of pain together. These methodological flaws tend to make interpretation and application of study results difficult to impossible.
More studies are needed to properly define the role of epidural steroid injections in low back pain and in sciatica. Despite this, most studies report that more than 50% of patients find measurable pain relief with epidural steroid injections. They also underscore the need for patients to enlist the services of professionals with extensive experience administering injections, and who always use fluoroscopy to ensure accurate placement.
Potential Benefits of Injections
Epidural steroid injections deliver medication directly (or very near) the source of pain generation. In contrast, oral steroids and painkillers have a dispersed, less-focused impact and may have unacceptable side effects. Additionally, since the vast majority of pain stems from chemical inflammation, an epidural steroid injection can help control local inflammation while also "flushing out" inflammatory proteins and chemicals from the local area that may contribute to and exacerbate pain. This article provides an overview of epidural steroid injections.
How Epidural Steroid Injections Work
An epidural steroid injection delivers steroids directly into the epidural space in the spine. Sometimes additional fluid (local anesthetic and/or a normal saline solution) is used to help ‘flush out’ inflammatory mediators from around the area that may be a source of pain.
The epidural space encircles the dural sac and is filled with fat and small blood vessels. The dural sac surrounds the spinal cord, nerve roots, and cerebrospinal fluid (the fluid that the nerve roots are bathed in).
Typically, a solution containing cortisone (steroid) with local anesthetic (lidocaine or bupivacaine), and/or saline is used.
A steroid, or cortisone, is usually injected as an anti-inflammatory agent. Inflammation is a common component of many low back conditions and reducing inflammation helps reduce pain. Triamcinolone acetonide, Dexamethasone, and Methylprednisolone acetate are commonly used steroids.
Lidocaine (also referred to as Xylocaine) is a fast-acting local anesthetic used for temporary pain relief. Bupivacaine, a longer lasting medication, may also be used. Although primarily used for pain relief, these local anesthetics also act as ‘flushing’ agents to dilute the chemical or immunologic agents that promote inflammation.
Saline is used to dilute the local anesthetic or as a ‘flushing’ agent to dilute the chemical or immunologic agents that promote inflammation.
Epidural Steroid Injections Control Inflammation
Epidural injections are often used to treat radicular pain, also called sciatica, which is pain that radiates from the site of a pinched nerve in the low back to the area of the body aligned with that nerve, such as the back of the leg or into the foot. Inflammatory chemicals (e.g. substance P, PLA2, arachidonic acid, TNF-α, IL-1, and prostaglandin E2) and immunologic mediators can generate pain and are associated with common back problems such as lumbar disc herniation or facet joint arthritis. These conditions, as well as many others, provoke inflammation that in turn can cause significant nerve root irritation and swelling.
Steroids inhibit the inflammatory response caused by chemical and mechanical sources of pain. Steroids also work by reducing the activity of the immune system to react to inflammation associated with nerve or tissue damage. A typical immune response is the body generating white blood cells and chemicals to protect it against infection and foreign substances such as bacteria and viruses. Inhibiting the immune response with an epidural steroid injection can reduce the pain associated with inflammation.