Prevalence of ossification of posterior longitudinal ligament in patients with ankylosing spondylitis.

Abstract

To determine the prevalence of ossification of the posterior longitudinal ligament (OPLL) in patients with ankylosing spondylitis (AS). A cross-sectional radiological examination was performed in patients diagnosed with AS. A bone and joint radiologist screened and confirmed the cervical radiographs of these patients. A review of the medical records was also conducted to investigate the relationship between the clinical manifestations and the actual expression of OPLL in patients with AS. Among 544 patients with AS, 470 (86.4%) were men and 96.1% were HLA-B27-positive. The mean age was 34.3 +/- 9.3 years and mean disease duration was 12.4 +/- 7.2 years. After reviewing the cervical radiographs, OPLL was found in 19 patients (3.5%; 95% CI 1.9, 5.0). The mean age of these 19 patients was 39.9 +/- 10.7 years, and the male to female ratio was 18:1. Interestingly, a statistically significant number of patients who expressed OPLL were older (p = 0.007). However, we were unable to determine whether OPLL was significantly associated with AS disease duration, peripheral arthritis, anterior uveitis/iritis, HLA-B27, anterior atlantoaxial subluxation, diffuse idiopathic skeletal hyperostosis, or other paraspinal ligament disorders. Our study showed that the frequency of OPLL in Korean patients with AS was 3.5%, which was considerably lower than previously reported values (15.5% in 103 Mexican AS). We were able to determine that OPLL in AS was associated with older age.