THE VALUE OF THE PROVOCATION RESPONSE IN LUMBAR ZYGAPOPHYSEAL JOINT INJECTIONS

Objective: To determine the relationship between pain provocation and the analgesic response in lumbar zygapophyseal joint blocks. Design: Consecutive patients undergoing intraarticular zygapophyseal joint blocks for the investigation of low back pain were included in this prospective study. Setting: The referred sample was from the metropolitan areas of New Orleans and San Francisco. Patients: Ninety patients with low back pain of >3 months' duration and no history of lumbar surgery. Interventions: All patients underwent one or more intraarticular injections of radiographic contrast followed by lignocaine (lidocaine) 2% into zygapophyseal joints between L2-3 and L5-S1. Those with definite responses at one or more levels underwent confirmatory blocks using 0.5% bupivacaine. Outcome measures: Provocation of familiar pain and relief of pain after the injection of local anesthetic. Patients were assessed by an independent observer. Results: A total of 203 joints were studied. Adopting liberal criteria, either exact or similar reproduction of pain on the one hand correlated with either definite or complete relief of pain after a single, analgesic block on the other (p < 0.0001). However, when more stringent criteria were adopted, such as response to a confirmatory block using bupivacaine, there was no significant association. Conclusions: This study calls into question the validity of pain provocation alone as a criterion standard in patients undergoing diagnostic lumbar zygapophyseal joint blocks.