Transforaminal vs. interlaminar epidural steroid injections: both offered similar pain relief, function for radiating low-back pain


Two commonly delivered epidural injection modalities deliver minimal differences in pain relief and function at one and six months, new research shows. Results presented at the 30th Annual Meeting of the American Academy of Pain Medicine indicate both injection types were effective for treating unilateral lumbosacral radicular pain.

”These results suggest that the difference in efficacy between these two modalities may be less significant than previously thought,” says lead study author George Chang Chien, Rehabilitation Institute of Chicago, USA. “Some slight differences were found earlier in the treatment process.”


Low-back pain that radiates to a lower extremity (ie., unilateral lumbosacral radicular pain) is a challenging condition to treat. Epidural injections, which deliver steroids into the epidural space around spinal nerve roots to reduce inflammation and pain, are commonly used in the United States, although assessing their effectiveness has proved difficult due to variations in techniques and patient selection, among other factors (Manchikanti et al, Pain Physician 2013; 16:E349-64).


Mindful of the lack of studies that compare treatments, investigators performed a systematic literature review to assess pain relief and functional improvement in transforaminal epidural steroid injections and interlaminar epidural steroid injections for unilateral lumbosacral radicular pain. During transforaminal epidural steroid injections, a long-acting steroid is injected into the opening at the side of the spine where a nerve roots exits, known as the neuroforamen. During interlaminar epidural steroid injections, an injection is delivered to the dorsal epidural space between the lamina of the vertebrae.


“It is thought that transforaminal epidural steroid injections provide better results due to the close deposition of medication to the site of nerve entrapment,” Chang Chien says. “Yet, existing studies have shown conflicting results. This review assessed all the high quality studies that directly compared the two commonly performed interventions.”


Studies met the Cochrane Review criteria for randomised trials and the Agency for Healthcare Research and Quality criteria for observational studies. Five studies assessed were prospective and three were retrospective, altogether encompassing 506 patients. A difference in pain reduction of ≥20% and functional score improvement of ≥10% were considered clinically significant.


At two weeks, transforaminal epidural steroid injections were superior to interlaminar epidural steroid injections in pain relief by 15%. However, at one or six months, no difference was found. Furthermore, combining pain improvements from all five prospective studies revealed < 20% difference between transforaminal epidural steroid injections and interlaminar epidural steroid injections (54.1% vs. 42.7%).


Results comparing functional improvements between groups showed slight superiority for interlaminar epidural steroid injections (56.4%) vs. transforaminal epidural steroid injections (49.4%) at 2 weeks and very slight differences for combined data (transforaminal epidural steroid injections 40.1% and interlaminar epidural steroid injections 44.8%).


Current practice trends have demonstrated a shift away from interlaminar epidural steroid injections, toward the increasingly more widespread practice of the transforaminal approach (Manchikanti et al, Pain Physician 2013; 16:E349-64).


“In part, this is due to the belief of superior efficacy,” Chang Chien explains. “This perceived superiority of transforaminal epidural steroid injections is accompanied by potential additional risks, likely to be much less common with interlaminar epidural steroid injections, such as intradiscal and intravascular injection with the attendant sequelae.”


Most complications from epidural injections are minor, but some can be serious, including the potential for neurological damage (Chang Chien et al, Pain Physician 2012; 15: 515-23). This begs the question as to whether the increased risk of potential catastrophic morbidity is effectively offset by the minimal differences in efficacy between the two respective approaches.


“Future well-designed studies are necessary to confirm the findings of this systematic review,” says Chang Chien. “We are in the process of starting this study soon.”