Objective:To identify the potential impact of cervical spine kyphosis on muscle parameters, the correlation between life quality score and muscle parameters, the correlation between cervical sagittal parameters and muscle parameters.Methods:From September 30, 2019 to September 30, 2020, 30 patients diagnosed with cervical kyphosis and 34 volunteers with normal cervical curvature were enrolled in this case control study. Kyphosis group and control group were matched with sex (χ 2=0.23, P=0.75), age ( t=0.13, P=0.73), BMI ( t=0.26, P=0.20) and neck pain duration time ( t=4.67, P=0.68). Visual analogue scale (VAS) and the neck disability index (NDI) were applied. Cervical sagittal parameters and cervical range of motion (ROM) were measured on lateral radiographs of cervical spine, which included C 2-C 7 lordosis (CL), cervical sagittal vertical axis (C 2-C 7 SVA), T 1-slope (T 1S) and spinal canal angle (SCA). To evaluate muscle functions, Co-contraction ratio (CCR) was measured by surface electromyography (SEMG). Spearman method was used to analyze the correlation between life quality score, cervical sagittal parameters and CCR. Results:VAS in control group 1.4±0.9 was lower than that in kyphosis group (2.3±0.7), and therewasno statistically significant difference ( t=3.71, P=0.30). NDI in control group (4.3%±2.5%) was significantly lower than that in kyphosis group (5.8%±1.7%), and the difference was statistically significant ( t=2.60, P=0.04). CL in control group (-18.76°±2.43°) was significantly lower than that in kyphosis group (13.80°±7.59°) ( t=3.43, P<0.01). SCA in control group (85.94°±4.52°) was significantly higher than that in kyphosis group (84.07°±10.44°) ( t=0.95, P<0.01). T 1S in control group (24.00°±2.85°) was significantly higher than that of kyphosis group (15.47°±11.33°) ( t=4.25, P<0.01), and C 2-C 7 SVA of control group (30.35±6.59 mm) was significantly higher than that in kyphosis group (19.08±14.47 mm) ( t=4.09, P<0.01). ROM in control group (50.23°±3.07°) was significantly higher than that in kyphosis group (45.63°±11.73°) ( t=2.21, P<0.01). CCR from neutral to flexion movement (CCRNF) was significantly lower in control group (0.46±0.20) than kyphosis group (0.84±0.13)( t=12.61, P=0.005), CCR from extension to neutral movement (CCREN) was significantly lower in control group (0.55±0.21) than in kyphosis group (0.79±0.16) ( t=7.10, P=0.042). CCRNF was significantly correlated with VAS ( r=0.504), NDI ( r=0.322), CL ( r=-0.240), T 1S ( r=-0.591), C 2-C 7 SVA ( r=-0.474) and ROM ( r=-0.303, P<0.05). There were significant correlations between CCREN and VAS ( r=0.339), NDI ( r=0.243), CL ( r=-0.347), T 1S ( r=-0.341), C 2-C 7 SVA ( r=-0.346) and ROM ( r=-0.065) ( P<0.05). However, there was no significant difference between CCR and SCA ( P>0.05). Conclusion:SEMG canbe an objective tool to evaluate the degree of neck pain and neck disability index. During cervical flexion movement, patients with cervical kyphosis had more tensional cervical extensor muscle and worse muscle function.

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.