Association between ossification of the posterior longitudinal ligament and ossification of the nuchal ligament in the cervical spine

OBJECTIVES: To investigate the association between ossification of the posterior longitudinal ligament (OPLL) and ossification of the nuchal ligament (ONL) in terms of incidence and size. METHODS: This retrospective study evaluated 297 patients who underwent CT of the cervical spine (C-spine). Two radiologists worked in consensus. The incidence of OPLL from patients with and without ONL was compared using Chi Square tests. The mean lengths of ONL from patients with and without OPLL were compared using Student t-test. The correlations between the length of ONL and the presence of OPLL and between the length of ONL and the length of OPLL were analyzed with Pearson correlations. RESULTS: We found that OPLL occurred more frequently in patients with ONL than in patients without ONL (odd ratio = 2.524, p = 0.037); however, the mean length of ONL did not differ significantly patients with and without OPLL (p = 0.874). We found no significant correlation between the length of ONL and the length of OPLL (p = 0.233). CONCLUSION: The presence of ONL was associated with the presence of OPLL. The length of OPLL and ONL showed no correlation.