The Study Of Sagittal Kinematic Characteristics On Adult Men's C2-C7 Vertebrae During The Extension-flexion

Backgrounds and ObjectivesTraditionally range of motion(ROM) and instantaneous centre of rotation(ICR) are used to describe the cervical spine movement from extension to flexion.They are performed with only end position radiographs.However,these radiographs fail to explain how the elaborate movement happens.The aim of the study was to confirm the interesting manifestation observed in the dynamic images of the cervical spine movement from full-extension to full-flexion.To further explore the fine motion of total process of cervical spine movement with the new concept of Cobb angular velocity(CAV).Methods1.Inclusion criteria: skeletally mature male,age 25 to 30 years.Exclusion criteria: neck pain,cervical congenital disorder,ossification of ligament,trauma,infection,tumor,deformity,inflammation,degenerative disk disease,instability,surgery,and other related cervical spine disease.A total of 12 skeletally mature male subjects(average age,27.0 0.8 years) were recruited in this research.2.Acquisition of the Dynamic Images of Cervical.A newly designed robotic DSA system(Artis_one XA 82008;Siemens Medical Solution,Germany)was installed to get the dynamic images of the cervical spine movement from full-extension to full-flexion.Subjects were fixed in the C-arm of the DSA system with their hands grasping the rear legs of the chair to help themselves pull down the shoulders and keep stable.They were informed to achieve the movement of cervical spine from full-extension to full-flexion when the DSA system was working to capture the continuous images.A series of continuous images(CI)of each cervical spine segment were collected.3.Images Processing.The continuous images collected from the DSA system were transferred into a separate e Film Workstation software(v.4.0,Merge Healthcare)and processed into static lateral radiographs.The centroid point as the geometric centre of C7 was marked in the static lateral radiograph and the midpoint of C2 inferior endplate was also marked by the Photoshop CS4(v 11.0,Adobe).Then,we overlapped the C7 cervical vertebral in all static lateral radiographs of each subject to get the dynamic images of the cervical spine movement from full-extension to full-flexion.4.Cobb Angular Velocity.Cobb angular velocity(CAV) as a revolving angle changing rate was defined as difference of Cobb angle between adjacent vertebrae in each equal part of total motion from full-extension to full-flexion.5.Dividing the Total Motion into Five Equal Partitions.In our study,the centroid point of each C7 was marked as “O'' and the midpoints of C2 inferior endplate in the end positions were marked as ‘‘A'' and ‘‘F'' separately.After overlapping all C7 cervical vertebrae of lateral radiographs,two lines were drawn through the point ‘‘O'',‘‘A'',and ‘‘O'',“F'',respectively.The angle between the two lines(?AOF)was measured and recorded as ?°.Then we divided the ?AOF into five equal partitions and got ?AOB =?BOC =?COD =?DOE =?EOF = 0.2?°.The points ‘‘B,'' ‘‘C,'' ‘‘D,'' and ‘‘E'' were the midpoints of C2 inferior endplate in corresponding lateral radiographs Results1.Base on the dynamic images got from the DSA system,we can figure out the average ROM values in different segments of cervical spine.The greatest extension–flexion motion occurred in C5/6 segment and the least in C2/3.2.Base on the dynamic images got from the DSA system,we can figure out the average CAV values in the 5 equal partitions of the total motion process of cervical spine from full-extension to full-flexion.There were significant differences of CAV values among the different segments from C2/3 to C6/7 in 1/5,2/5,3/5,4/5 and 5/5 partitions in the total process of cervical spine movement(C2/3,F=6.707,P=0.003;C3/4,F=10.081,P=0.003;C4/5,F=26.462,P<0.001;C5/6,F=15.562,P<0.001;C6/7,F=44.812,P<0.001).3.A broken line graph(Figure 3)was created based on the data in Table 2.We found that different segments had its own unique kinematic characteristics during the flexion.Conclusions1.Define a new concept of Cobb angular velocity(CAV) to further explore the fine motion of total process of cervical spine movement.2.The intervertebral movements of various cervical segments did not take a uniform motion when cervical spine moved from full-extension to full-flexion.3.The C4/5 and C5/6 segments exhibited more complex kinematic characteristics in sagittal orientation in the view of CAV.4.We had a hypothesis that there was a positive correlation between injury/ degeneration and complexity of the intervertebral movement in the view of CAV.