Measurement of clivus-axial angle and correlation between clivus-axial angle and cervico-medullary angle in Chinese population / 中华骨科杂志

ABSTRACT

Objective To measure the clivus-axial angle (CAA) of Chinese,provide a normal value,and explore the correlation between CAA with cervico-medullary angle (CMA).Methods The CAA was measured on the CT of cervical spine in 225 Chinese with normal cranio-vertebral junction (CVJ).Both the CAA and the CMA were measured on the MRI of cervical spine in 117 subjects.All measurements were performed under a bone window (window level,300 Hu; window width,1 000 Hu) with an accuracy of 0.01°.A regression analysis was used for analyzing the correlation between CAA and CMA.The angle between the clivus plane and the straight line parallel to that of the posterior margin of the C2 vertebral body was defined as CAA; moreover,the angle between the strajght line parallel to the ventral side of the cervical spinal cord and the straight line parallel to that of the ventral side of the medulla oblongata was defined as CMA.Two experienced spinal surgeons performed the measurements.The CAA and CMA were measured three times,and the mean value was considered as the result.Results The CAA of 225 subjects was 133.52°-172.16° (156.93°±6.53°).The 95％ confidence interval was 145.10°-170.19° in male and 142.67°-168.47° in female.If the patients were divided into five groups according to their age,a comparison of these groups showed that there were no significant differences among the groups with respect to CAA.It showed that there was consistency between the CAAs measured with MRI and CT.The CMA for 117 patients ranged from 130.38° to 168.75° with a mean value of 154.17°±6.54°,and its 95％ confidence interval ranged from 141.35° to 166.99°.If the patients were distributed according to their gender or to their age,there were no significant differences among the groups.The relationship between CAA and CMA was linearity,and the regression coefficient was as high as 0.95 (P=0.007).Conclusion The normal CAA of Chinese is from 133.52° to 172.16°.The 95％ confidence interval goes from 145.10° to 170.19° in male,and 142.67° to 168.47° in female,close to CMA.It is valuable for measuring the compression of spinal cord,which can be accessed easily during the procedure.