Interlaminar versus transforaminal epidural steroids for the treatment of subacute lumbar radicular pain: a randomized, blinded, prospective outcome study.

BACKGROUND There is uncertainty in the literature over the relative effectiveness of lumbar epidural interlaminar (IL) steroid injection versus transforaminal (TF) steroid injection for lumbar radiculopathy. Most studies to date have been retrospective, or technically focused. OBJECTIVE To complete a randomized, blinded, prospective outcome study of the short-term benefit for IL versus TF epidural steroids for the treatment of subacute lumbar radicular pain. STUDY DESIGN Prospective, randomized, blinded, subacute efficacy trial. SETTING Tertiary care pain management center, major metropolitan city, United States. METHODS After institutional review board approval, 42 age-matched patients with similar lower back pain and unilateral radicular symptoms were enrolled and randomized in a patient and evaluating physician blinded trial to IL or TF epidural steroids from 2007 through 2009. Prior to intervention and 10-16 days after injection, each participant was evaluated by questionnaire and physical exam by an independent physician. All injections were performed by the same physician. Thirty-eight participants completed the study, 18 in the IL group and 20 in the TF group. Four participants required a repeat injection, and 2 participants crossed over to the alternative injection type (IL to TF). RESULTS Overall, physical exam, diagnostic testing, disability, activity, depression measures, and opioid pill use were similar between the 2 groups, both pre-injection baseline and post-injection improvement. In primary outcomes, the post-injection follow-up Numeric Rating Scale (NRS) was more greatly reduced in the TF group. The NRS decreased from 7.0 ± 1.9 to 3.9 ± 3.1 (mean values +/- standard deviation) in the IL group and 6.4 ± 2.1 to 1.7 ± 1.4 in the TF group. The Oswestry Disability Index was reduced from 37.5 ± 12.6 to 19.0 ± 16.7 in the IL group and 38.3 ± 6.4 to 21.6 ± 16.8 in the TF group. In secondary outcomes, the depression scale was reduced from 4.39 ± 3.22 to 2.28 ± 3.20 in the IL group and 4.10 ± 1.94 to 1.65 ± 1.63 in the TF group. Walking tolerance was increased from 8.1 ± 4.6 blocks to 10.6 ± 4.4 in the IL group and 8.9 ± 5.3 blocks to 11.8 ± 4.2 in the TF group. LIMITATIONS The study did not examine long-term outcomes. A single experienced interventionalist performed all injections. CONCLUSION Results suggest that patients may experience greater subjective relief, at least initially, from TF epidural steroid injections over IL. However, more objective, and likely subacute, therapeutic effects are similar.