Chronic cervical zygapophysial joint pain after whiplash. A placebo-controlled prevalence study.

STUDY DESIGN The authors developed a diagnostic double-blindfolded survey using placebo-controlled local anesthetic blocks. OBJECTIVE To determine the prevalence of cervical zygapophysial joint pain among patients with chronic neck pain (more than 3 months' duration) after whiplash injury. SUMMARY OF BACKGROUND DATA The prevalence of cervical zygapophysial joint pain after whiplash has been studied by means of comparative local anesthetic blocks. The concern is that such blocks may be compromised by placebo responses and that prevalence estimates based on such blocks may exaggerate the importance of this condition. METHODS Sixty-eight consecutive patients referred for chronic neck pain after whiplash were studied. Patients with dominant headache were first screened with the use of comparative blocks of the C2-C3 zygapophysial joint. Patients who had positive responses concluded investigations. Those who did not experience pain relief together with the patients with dominant neck pain proceeded to undergo placebo-controlled local anesthetic blocks. Two different local anesthetics and a placebo injection of normal saline were administered in random order and under double-blindfolded conditions. A positive diagnosis was made if the patient's pain was completely and reproducibly relieved by each local anesthetic but not by the placebo injection. RESULTS Among patients with dominant headache, comparative blocks revealed that the prevalence of C2-C3 zygapophysial joint pain was 50%. Among those without C2-C3 zygapophysial joint pain, placebo-controlled blocks revealed the prevalence of lower cervical zygapophysial joint pain to be 49%. Overall, the prevalence of cervical zygapophysial joint pain (C2-C3 or below) was 60% (95% confidence interval, 46%, 73%). CONCLUSION Cervical zygapophysial joint pain is common among patients with chronic neck pain after whiplash. This nosologic entity has survived challenge with placebo-controlled, diagnostic investigations and has proven to be of major clinical importance.