Epidural Steroid Injections: Section 1

Introduction
There have been numerous studies on the use of epidural corticosteroids for treating spinal pain, but few controlled clinical trials. Despite the lack of universal acceptance, they are commonly used to treat both radicular and axial pain resulting from lumbar disc disease.

Rationale
There is abundant evidence suggesting that inflammatory mediators are important in both radicular and axial pain syndromes (15).

Kawakami, et al. Experimental lumbar radiculopathy. Behavioral and histologic changes in a model of radicular pain after spinal nerve root irritation with chromic gut ligatures in the rat. Spine 1994 Aug 15;19(16)1795-802.

Kawakami, et al. Experimental lumbar radiculopathy. Immunohistochemical and quantitative demonstrations of pain induced by lumbar nerve root irritation in the rat. Spine 1994 Aug 15;19(16)1780-94.

Epidural corticosteroids have a number of effects on the inflammatory process, which is the primary rationale for their use in spinal pain syndromes.

Lee, et al. The role of steroids and their effects on phospholipase A2: an animal model of radiculopathy. Spine 1998;23(11):1191-96.

In addition to relieving inflammation, corticosteriods have membrane stabilizing effects (6). An important component of their mechanism of action, then, may be a local anesthetic effect.

Local anesthetic agents are frequently combined with epidural corticosteroids. An obvious benefit of doing so is that pain relief, even if short lasting, may provide psychological benefit. However, there is some evidence that, in addition to this short term benefit, local anesthetics can provide long term relief.

Derby, et al. Precision percutaneous blocking procedures for localizing spinal pain. Part 2: The lumbar neuraxial compartment. Pain Digest 1993;3:175-88. Ref 19.

There is experimental evidence supporting the use of epidural steroids for radiculopathy.

Hayashi, et al. The effect of epidural injection of betamethasone or bupivicaine in a rat model of lumbar radiculopathy. Spine 1998;23(8):877-85.

A number of studies have been done on the efficacy of epidural steroid injections for radicular pain. In general, these have consisted of uncontrolled case studies or trials in which 33% to 77% of injected patients reported pain reduction (4,8, Weinstien, Barnsely).

Weinstein, et al. Epidural steroid injections. Spine 1995;20:1842-6.

Commentary. Barnesly. Pain Medicine Journal Club Journal 1996;1(4):212-14.

Carette recently published a randomized, controlled, double-blind trial on the efficacy of epidural steroid injections in patients with sciatica and CT evidence of a herniated disc.

Carette, et al. Epidural corticosteroid injections for sciatica due to herniated nucleus pulposus. NEJM 1997;336:1634-40.

In his study, the patients treated with epidural steroids showed short-term improvement in pain control and sensory deficits compared with epidural normal saline. The differences between treatment and control groups faded over time, leading Carette to conclude that ESIs offer no long-term benefit in function or need for surgical intervention.

Carette, et al. Epidural corticosteroid injections for sciatica due to herniated nucleus pulposus. NEJM 1997;336:1634-40.

Carette’s conclusions are questionable for a number of reasons.

Commentary. Bogduk. Pain Medicine Journal Club Journal 1998;4(1):29-31.

Commentary. The Back Letter 1997;12(7):75

Commentary. Karasek. The Back Letter 1997;12(9):100

First, as the mean duration of symptoms prior to initiation of therapy was 13 weeks his study did not address the efficacy of epidural steroid injections on acute radiculopathy. More importantly, his study included no structured co-interventions. A retrospective study by Saal, et al, showed that combining a comprehensive rehabilitation program with judicious use of epidural steroid injections yields a 90% good to excellent outcome (with a 92% return-to-work rate) in patients with lumbar radiculopathy (14). This supports the use of epidural steroid injections in relieving pain and restoring function, when they are used to facilitate a rehabilitation program rather than as a sole intervention.