Nancy A. Melville

March 10, 2014

PHOENIX, Arizona — Transforaminal epidural steroid injections, despite being widely regarded as superior to interlaminar injections, are not significantly superior in providing pain relief or functional improvement for radiating low back pain, a new systematic review of trials shows.

"I think these findings are definitely controversial, but I have had numerous people say to me that this is in fact very consistent with their experience using these two modalities," said lead author George Chang Chien, DO, from the Rehabilitation Institute of Chicago, Illinois.

Study results were presented here at the American Academy of Pain Medicine (AAPM) 30th Annual Meeting.

Epidural Injections

Epidural injections, which deliver steroids into the epidural space around spinal nerve roots to reduce inflammation and pain, have become highly popular in the United States for the management of chronic pain.

While transforaminal injections are typically favored in clinical practice as the more effective modality, they are associated with potentially severe adverse effects that are less common with interlaminar epidural steroid injections, including intradiscal and intravascular injection.

For the study, Dr. Chang Chien and his colleagues evaluated data on 8 trials, including 5 prospective and 3 retrospective studies, comparing transforaminal and interlaminar epidural steroid injections for the treatment of unilateral lumbosacral radicular pain from Cochrane Central Register of Controlled Trials, PubMed, and Scopus databases.

The studies involved a combined total of 506 patients, including 249 (49%) who were followed up for an average of 3.2 months.

Those receiving transforaminal epidural steroid injections showed about a 15% greater improvement for short-term pain relief after 2 weeks; however, at longer-term follow-up of 1 or 6 months, no significant differences were seen between the 2 approaches.

The combined measures of pain improvement in the 5 prospective studies showed a less than 20% difference between transforaminal and interlaminar epidural steroid injections (54.1% vs 42.7%).

In terms of functional improvement, the interlaminar injection groups showed slightly better results than transforaminal at 2 weeks (56.4% vs 49.4%, respectively); however, the differences in combined data on the 2 approaches were only slight (44.8% for interlaminar and 40.1% for transforaminal).

"These results suggest that the difference in efficacy between these 2 modalities may be less significant than previously thought," Dr. Chang Chien said.

While there have been numerous studies on the effectiveness of each of the modalities, issues including patient selection, methods, and outcome measures have somewhat clouded results, as described in a recent health policy review (Pain Physician. 2013;16:E349-64).

Dr. Chang Chien noted that the issues make it even more difficult to try to directly compare the transforaminal with the interlaminar approach.

"We used tight criteria to try to answer an important clinical question. Thus, one limitation of our study includes that the sample is relatively small, but what that indicates is that there haven't been any solid studies to compare the 2 approaches head-to-head — and that's important."

Placebo-Controlled Studies

The evidence behind the preference for transforaminal injections, though flawed, is backed by stronger placebo-controlled studies supporting the approach, explained Stephen Cohen, MD, a professor of anesthesiology and critical care medicine at Johns Hopkins University, Baltimore, Maryland.

"The results of comparative studies, though nearly all are underpowered and many contain methodological flaws, suggest that transforaminal injections may be more effective than interlaminar injections," he told Medscape Medical News. "This is consistent with placebo-controlled studies evaluating epidural steroid injections, in which a higher proportion of those studies evaluating transforaminal injections are positive than those evaluating interlaminar injections."

He added that finding that transforaminal injections had greater short-term improvement in fact could be important in terms of longer-term outcomes.

"The evidence for short-term relief — less than 6 weeks — with epidural steroid injections is strong, [and the] injections may also provide long-term relief by allowing patients to resume their normal activities and participate in physical therapy or therapeutic exercise programs," Dr. Cohen said. "In this regard, the better short-term pain relief is important."

The adverse effects associated with each modality are complex, both doctors noted.

"The risks are higher for all transforaminal injections, but the increased risk is considerable in the cervical, thoracic, and upper lumbar regions," Dr. Cohen said. "It is likely higher for lower lumbar injections, but the increased risk is minimal in patients who have not had previous surgery."

Furthermore, those risks need to be weighed against the increased benefits, he noted. "For instance, some people who fail epidural steroid injections will end up being placed on opioid therapy or have surgery, which are much riskier than transforaminal epidural steroid injection."

Interlaminar epidural steroid injections are meanwhile safer in the neck and thoracic region and are ideal for those with bilateral symptoms, Dr. Cohen added. "One can do bilateral transforaminal steroid injections for bilateral symptoms, but of course the risks double," he said.

He additionally noted that the risk for a spinal headache with an interlaminar epidural steroid injection is much higher in patients who have undergone previous surgery.

In terms of the general risk associated with transforaminal injections, Dr. Chang Chien added that many can be avoided with simple preventive measures.

"I think what's important is that the risk associated with transforaminal injections can be mitigated. Some of the biggest concerns, such as the paraplegia, seizures, or death have been attributed to the use of certain medications. Risk mitigation should be the top priority when planning for an elective procedure with best evidence demonstrating short- to intermediate-term efficacy."

"We are conducting the definitive study that addresses the methodological flaws found in previous studies to confirm the findings of this systematic review," he added.

The authors and Dr. Cohen have disclosed no relevant financial relationships.

American Academy of Pain Medicine (AAPM) 30th Annual Meeting 30th Annual Meeting. Abstract 130. Presented March 7, 2014.

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