Can Topical Anesthetic Reduce the Pain Associated with Diagnostic Blocks of the Lumbosacral Spine?

Objective.  To evaluate the effectiveness of a topical local anesthetic cream (5% liposomal lidocaine) in reducing needle‐induced pain in patients investigated for suspected zygapophysial (z‐joint) or sacroiliac (SI) joint pain. Design.  Triple‐blinded randomized controlled trial. Setting.  Interventional fluoroscopy suite. Study Population.  Eighteen patients presenting with chronic mechanical low back pain. Interventions.  Thirty minutes prior to diagnostic z‐ or SI joint blocks, equivalent amounts of topical 5% liposomal lidocaine cream was applied to one side of the low back and a placebo cream to the other. The treatment side and injection order were randomized and the patient, injectionist, and data recorder were blinded. Outcome Measures.  The subjects provided numerical rating scores of pain intensity immediately following each phase of the injection (skin penetration, deep, overall). Scores were analyzed with dependent t ‐tests. Results.  The injection associated pain was significantly less during the skin penetration phase on the side of the local anesthetic vs the placebo cream (3.0/10 vs 4.2/10; P  = 0.002). No significant differences were found during the deep phase or for the injection procedure overall. Conclusions.  Five percent liposomal lidocaine cream significantly reduces the pain associated with the skin penetration phase of lumbosacral diagnostic blocks but does not change the pain associated with the deep phase or the injection procedure overall. Its usefulness for this application is questionable.