Association between cervical curve and the cranio-cervical curve and ossification of ligaments in patients with cervical degenerative diseases / 中华骨科杂志

ABSTRACT

Objective:To explore the correlation between cervical curve and ossification of ligaments in cranio-cervical junction and cervical spine in patients with cervical degenerative diseases.Methods:A retrospective study was conducted among 458 patients with cervical degenerative disease who underwent cervical spine X-ray and CT examinations at the Orthopedics Department of Beijing Tiantan Hospital, Capital Medical University between January 2016 and July 2020. There were 265 males and 193 females, with an average age of 57.02±10.41 years (range, 22-87 years). Patients were divided into 5 types (lordosis, straight, S-type degenerative kyphosis, R-type degenerative kyphosis and C-type degenerative kyphosis). Cervical lordosis was defined as C 2-C 7 curve <-4°, cervical kyphosis was defined as >4°, cervical straight was defined as -4° to 4°. C 2-C 7 curve, C 0-C 2 curve were measured respectively, and correlations among these imaging parameters were analyzed. CT images were used to assess the presence of ossification of ligaments in cranio-cervical and cervical spine, including ossification of the posterior longitudinal ligament, nuchal ligament, ligamentum flavum, transverse ligament, apical ligament, diffuse idiopathic skeletal hyperostosis (DISH), as well as capped dens sign (CDS), and correlations between these cervical curve and presence of ossification of ligaments were analyzed. The different grades were based on the length of the ossification of interest with respect to the distance from the posterosuperior rim of the anterior arch of the atlas to the inferior margin of the foramen magnum on mid-sagittal cervical spine CT images, Grade 3 CDS was determined when the length was more than two-thirds. Results:There were 245 patients with cervical lordosis, 114 patients with straight, 53 patients with S-type degenerative cervical kyphosis, 36 patients with R-type degenerative cervical kyphosis and 10 patients with C-type degenerative cervical kyphosis. C 0-C 2 curve showed a negative correlation with C 2-C 7 curve in all enrolled patients ( r=-0.45, P<0.001) and R-type degenerative kyphosis group ( r=-0.58, P<0.001); C 0-C 2 curve showed no correlation with C 2-C 7 curve in lordosis ( r=-0.10, P=0.124), straight ( r=-0.11, P=0.233), S-type degenerative kyphosis ( r=-0.01, P=0.943) or C-type degenerative kyphosis groups ( r=0.03, P=0.946). CDS was detected in 38.4% (176/458) of patients, and Grade 3 was detected in 17.9% (82/458) of patients. The prevalence of CDS was correlated with R-type degenerative cervical kyphosis ( r=0.10, P=0.030). Cervical kyphosis, S-type degenerative kyphosis, C-type degenerative kyphosis, C 2-C 7 curve and C 0-C 2 curve showed no correlation with ossification of the posterior longitudinal ligament, nuchal ligament, ligamentum flavum, transverse ligament, apical ligament, diffuse idiopathic skeletal hyperostosis (DISH) or different grades CDS ( P>0.05). Conclusion:R-type degenerative cervical kyphosis are more likely to correlate with the cranio-cervical curve and CDS, which is an ossification of ligament in cranio-cervical junction.