In a randomized trial, these injections predicted response to radiofrequency denervation. For patients with chronic low back pain, lumbar facet blocks sometimes are used diagnostically (to predict response to a more definitive procedure, radiofrequency denervation) and sometimes are used therapeutically. Two types of lumbar facet blocks are injections of local anesthetic and steroid into facet joints (intra-articular injection) and injections into the area of the nerves supplying facet joints (medial branch block). In this complicated study, 229 patients with chronic low back pain, but without spinal stenosis or neurological findings, were randomized to receive intra-articular facet injections or medial branch blocks (both with bupivacaine plus steroid) or saline placebo. Patients in either active-treatment group were significantly more likely to experience immediate pain relief than were placebo recipients (≈55% vs. 30%); however, at 1 month, improvement in pain was minimal in all three groups. At that point, patients in active-treatment groups who had experienced immediate response to injection underwent radiofrequency denervation; all placebo recipients also were offered radiofrequency denervation. Three months later, patients who underwent radiofrequency ablation because they were immediate responders to facet or medial branch injections were twice as likely as placebo recipients to report significant pain relief (≈50% vs. 25%). |
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This study suggests that facet joint or medial branch injections have some diagnostic value as predictors of short-term response to radiofrequency denervation, but they have little therapeutic value themselves. Note, however, that the overall effectiveness of radiofrequency denervation was challenged recently: In a randomized trial, this procedure had no value when added to an exercise program (NEJM JW Gen Med Aug 15 2017 and JAMA 2017; 318:68).