Epidural injections of steroids may have only a small effect in preventing or delaying the need for spinal surgery for low back pain when compared to other treatments, according to a review and meta-analysis of several randomized controlled trials (RCT). The results were mixed: Injections reduced the need for surgery in some patients, but this effect was seen only in the short-term, up to one year, and may not be lasting.
The review article published in The Spine Journal by Bicket et al, evaluated the findings from 26 studies to determine whether epidural steroid injections (ESIs) have a surgery-sparing effect on patients with back pain. The studies evaluated in the article were found by searching through several databases, including Cochrane, PubMed, and EMBASE.
Meta-analysis was performed on the results of data from 22 studies on 2,251 patients. This analysis found that 18.2% of patients who received injections later needed surgery, compared to 20.3% of those patients who did not receive injections. However, this difference did not reach statistical significance for the entire cohort. There was a risk ratio of 0.92. When lower-quality studies were excluded, the risk ratio was 0.93. A risk ratio—the ratio between the risk seen in the intervention group and in the control group—is lower than 1.0, meaning the intervention decreases the risk of the outcome. The authors found only a moderate quality of evidence for the overall effect of epidural steroid injections.
Short-term reduction for surgery still significant
“The main finding in this study is that there may be a weak surgery-sparing effect for ESI in the short term but not the long term,” the authors concluded. They added that a short-term reduction in the need for surgery is still significant because they used a very liberal definition of the need for surgery. A more restrictive definition of the need for surgery might have produced a greater correlation, they said.
“In many ways, the ability to prevent surgery should represent a key outcome measure for ESI, as it is objective (whereas pain is always subjective), reflects sustained and long-term treatment failure, and can dramatically alter cost-utility analyses,” the authors wrote.
Low Back Pain a Leading Cause of Disability
Low back pain is a leading cause of disability and is estimated to cost more than $100 billion annually in the United States, according to the article. Epidural steroid injections are widely used as a treatment for back pain, but there have been few studies of whether they are cost effective. Because it is difficult to demonstrate whether these injections can help people with low back pain to return to work, the authors chose to determine if there was any evidence of reduction in a later need for surgical intervention.
The authors also performed a meta-analysis of data from subgroups, such as the cause of back pain (herniated nucleus pulposus, spinal stenosis, or foraminal narrowing) or the type of epidural steroid injection (caudal, transforaminal, or interlaminar). ESIs did not reduce the need for subsequent surgery in these subgroups.
Only one of the studies reviewed evaluated the effect of steroid injections as a primary outcome. It showed moderate evidence that the patients who received injections were less likely to undergo surgery than those who received control treatment.
Other studies examined surgery as a secondary outcome. These showed a trend toward a reduction in the subsequent need for surgery in the short term, up to 1 year after the epidural steroid injections. The risk ratio seen up to a year after treatment was 0.68, with a 95% confidence interval for the short term, but there was a risk ratio of 0.95 for surgery that occurred later than 1 year after the injections.
Control treatments in the studies that were reviewed or analyzed included injections of normal saline, lidocaine, or bupivacaine; inserting a needle but injecting nothing; bed rest; and nonsteroidal anti-inflammatory, muscle relaxants, or opioids.
Bicket MC, Horowitz JM, Benzon HT, Cohen SP. Epidural injections in prevention of surgery for spinal pain: systematic review and meta-analysis of randomized controlled trials. Spine J. October 13, 2014.