Chronic low back pain: The therapeutic benefits of diagnostic medial branch nerve blocks

Background: Chronic low back pain (CLBP) is an extremely prevalent disease, whose etiology is often multifactorial. Facet joint arthropathy is one of the most common causes of CLBP. Facet joints are innervated by the medial branches of the primary and adjacent level dorsal rami and are, therefore, key potential targets for the symptomatic management of CLBP. A lumbar medial branch nerve block (MBB) procedure is often used to assist in the diagnosis of facet mediated CLBP. For unclear reasons, some patients experience protracted relief of CLBP after diagnostic MBBs alone. Objective: To describe the phenomenon of protracted relief of CLBP after diagnostic MBBs and search for predictors of this response. Study Design: A retrospective chart review of patients who underwent MBB procedures by a single practitioner, over a 2 year period, was conducted. Setting: All patients were seen at the Montefiore Multidisciplinary Pain Program, Bronx, NY. Methods: Data from follow up visits was used to categorize patient’s response to MBBs as having no relief (NR), transient relief (TR) or protracted relief (PR). Patient demographics and characteristics were collected, and a multivariate analysis investigating associations with PR was conducted. Results: 146 patients met inclusion criteria. 41 patients (28%) had NR, 54 (37%) had TR, and 51 (35%) had PR. CLBP symptom duration of < 6 months (P = 0.013) and unilateral back pain symptoms (P = 0.0253) were significantly associated with PR after MBB. Limitation: This is a retrospective study with a relatively small sample size conducted on patients belonging to a single practitioner. Outcomes were based largely on subjective patient satisfaction scores. Conclusions: In select patients, MBB may produce protracted relief of CLBP symptoms. The authors present distinct hypotheses which may help explain the therapeutic effects of diagnostic MBB procedures.