| Background and objectivesA normal cervical sagittal alignment is essential for supporting the head and maintaining a forward gaze and has an auxiliary role in important physiological functions such as breathing and chewing.Cervical sagittal alignment parameters are often used in the diagnosis of cervical diseases,preoperative planning,postoperative assessment and prognosis evaluation.CT scans are commonly used to evaluate the Angle of sagittal kyphosis of the cervical spine.At present,CT scanning images are commonly employed for cervical sagittal lordosis measurement.However,for it’s sensibility of angulation of CT sagittal section plane and sigattal plane of cervical spine,malalignment of cervical spine on coronal plane and the subjective choice of section plane for measurement by the surveyor,the accuracy of cervical sagittal alignment parameters measurement on CT sagittal section is doubtful.The objective of this study is to develop a measurement method of cervical sagittal alignment parameters based on 3D medical imaging,evaluate its reliability,and compare it with CT sagittal section method to explore the influence of cervical scoliosis on the it’s accuracy.Methods and materials1.Medical image management software and CAD software were used to design a method based on 3D fitting planes for measurement of cervical sagittal alignment parameters.In order to evaluate the reliability of this method,cervical alignment parameters of 40 cases of CT scanning images repeated measured by three surveyors were applied to calculate the intraclass correlation coefficient(ICC)2.The researcher measured cervical sagittal alignment parameters of 168 cases of cervical CT scanning images respectively with fitting plane method and CT sagttial section method.The difference and correlation between the values gain from two methods by relevant statistical test.3.All the samples with a global or segmental cervical scoliosis angle greater than 50 were involved into scoliosis group and non-scoliosis group if not.The differences between the values gain from the two methods were calculated and statistically analyzed.Result1.The fitting plane method for cervical sagittal alignment parameters measurement was successfully developed.High ICCs(>0.90)of fitting plane method were revealed.2.The values of Cobb angle O-C7,Cobb angle O-C2,Cobb angle C2-C7 measured with fitting plane method and CT section method were significant different.There are significant moderate to strong correlation between the two methods,Cobb angle O-C2 is significantly negatively correlative with Cobb angle C2-C7.3.In scoliosis group,the differences between values of Cobb angle O-C7,Cobb angle O-C2 and Cobb angle C2-C7 gained from two methods were respectively 3.86°± 2.59°,3.31°± 3.77°,4.19°± 4.49°.These differences were 2.51°± 1.94°,3.12°±3.62°,2.77°±2.88° Differences between the values of Cobb angle O-C7 and Cobb angle C2-C7 measured with two methods showed significant difference between scoliosis group and non-scoliosis group.There were significant correlation between values’ difference of Cobb angle O-C7 and C2-C7 scoliosis angle,values’ difference of Cobb angle O-C7 and C4-C7 scoliosis angle,values’ difference of Cobb angle C2-C7 and C2-C4 scoliosis angle as well.Conclusion1.Compared with CT section method,fitting plane method is more representative of the true sagittal alignment parameters of cervical spine.Fitting plane method shows an excellent reliability.2.Differences of angles of cervical sagittal lordosis measured on fitting planes and CT sections indicted that it may not be accurate to evaluate those parameters on CT sections.There is a negative correlation between Cobb angle C2-C7 and Cobb angle O-C2.3.The global and segmental scoliosis of the cervical spine has influence on the accuracy of the measurement of sagittal cervical lordosis angle on CT sagittal section. |
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