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: C onsecutive patients undergoing intraarticular zygapophyseal joint bloc ks for the investigation of low back pain were included in this prospe ctive study. Setting: The referred sample was from the metropolitan ar eas of New Orleans and San Francisco. Patients: Ninety patients with l ow back pain of >3 months' duration and no history of lumbar surgery. Interventions: All patients underwent one or more intraarticular injec tions of radiographic contrast followed by lignocaine (lidocaine) 2% i nto zygapophyseal joints between L2-3 and L5-S1. Those with definite r esponses at one or more levels underwent confirmatory blocks using 0.5 % bupivacaine. Outcome measures: Provocation of familiar pain and reli ef of pain after the injection of local anesthetic. Patients were asse ssed by an independent observer. Results: A total of 203 joints were s tudied. Adopting liberal criteria, either exact or similar reproductio n of pain on the one hand correlated with either definite or complete relief of pain after a single, analgesic block on the other (p < 0.000 1). However, when more stringent criteria were adopted, such as respon se 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 undergo ing diagnostic lumbar zygapophyseal joint blocks.