Chronic Whiplash Associated Disorders (WAD): Responses to Nerve Blocks of Cervical Zygapophyseal Joints

Objective. This study explores the prevalence of facet joint pain in chronic Whiplash Associated Disorder (WAD). Design. Forty-seven patients with chronic WAD were scheduled for medial branch blocks of the cervical spine. Methods. The patient’s localization of the pain together with established pain maps guided to the first level of zygapophyseal joint to be tested. The joint was anesthetized by injecting bupivacaine (0.5 ml; 5 mg/ml) to the medial branches of the cervical dorsal rami above and below the joint. If a positive response was noted, the schedule continued with a double-blinded sequence with a placebo (saline) and bupivacaine. If a negative response was noted, other joint levels were anesthetized until all joints from C2 to C7 were tested. The responses were assessed using a visual analog scale (VAS) in a predefined protocol. The study was carried through with a definition of a positive response to a diagnostic block as a VAS decrease ≥50% compared with baseline during a minimum of 3 hours after the block. All other responses were regarded as negative. The data were also analyzed using a definition of a positive response as a VAS decrease ≥80%, and figures from this analysis are presented as the main result of the study. Results. The study yielded 29% true positive responders, 60% non-responders, and 11% placebo responders. Conclusions. A substantial amount of patients with chronic WAD have their persistent pain emanating from cervical zygapophyseal joints.