Analysis of Radiography Findings of Ossifi cation of Nuchal Ligament of Cervical Spine in Patients With Cervical Spondylosis

Study Design. Retrospective clinical data analysis. Objective. This study was conducted to investigate the incidence, related factors, and radiography findings of ossification of the nuchal ligament (ONL) in patient with cervical spondylosis, which could serve as a basis for further studies of the relationships between ONL and cervical spondylosis. Summary of Background Data. Injury to nuchal ligament, which might cause ONL, may aggravate cervical spine instability, leading to cervical spondylosis. Thus, it is important to understand the characteristics of ONL in patients who are diagnosed with cervical spondylosis. Methods. Medical records of 372 patients with cervical spondylosis were reviewed. Data analysis included patients' sex, age, location and classification of ONL, and ossification of the posterior longitudinal ligament (OPLL). Radiological features were evaluated by lateral plain radiography and computed tomography for 2-dimensional sagittal plane reconstruction. Results. Of the 372 patients with cervical spondylosis, 49.7% had a diagnosis of ONL; the incidence of ONL was higher in males than in females (P = 0.001) and in elderly patients than in young patients (P = 0.005). The varying pictures of ONL on the plain radiography were classified into 5 types: local, continuous, segmental, mixed, and unclassified, and the distribution was 49.7%, 33.0%, 3.2%, 8.6%, and 5.4%, respectively. ONL occurred mostly at the level of C-4,C-5 (75.7%) and C-5,C-6 (81.1%). The incidence of ONL was higher in patients with OPLL than others (P < 0.001), and the incidence of multilevel ONL was higher in patients with OPLL than in patients with ONL only (P = 0.038). Conclusion. The incidence of ONL is 49.7% in patients with cervical spondylosis. Sex, age, and OPLL are related factors of ONL. ONL can be classified into different types through morphology. Local type is the most common type of ONL, and multilevel ONL occurs mostly in patients with OPLL. C-4,C-5 and C-5,C-6 are the levels where ONL occurs mostly. Level of Evidence: 4