Imageologic Study On The Anatomic Parameters And The Movement Of The Cervical Spine In Chinese Subjects

Flexibility and stability are the two features of spinal column. It is developed gradually in the evolutionary process of human being for some kind of requisition and function. Therefor, a stable but not flexible spinal column can not realize it's normal function. Subtotal corpectomy is used for the treatment of many kinds of diseases of cervical spine clinically, and after that, cervical spine reconstruction of stability is need. In the meantime, that remaining normal movement of the intervertebral and to avoid acceleratement of cataplasia of the closer segement is very important. To attaine this purpose, our research group has designed and manufactured artificial cervical joint complex (ACJC). We also have done biomechanical test and preliminary assessment about the stability and movement of the cervical spine in the vitro [1]. However, ACJC is a preliminary study, there are many aspects which need to be improved [2]. Some of these problems are: there are no well-defined parameters about anatomy and movement of the cervical spine. But there are few study about the parameters about anatomy in our country. And the movement of cervical spine is multiplicity. Until now, we do not know the couple mode and couple degree.Objective: To measure the height of vertebral body and intervertebral disk of the cervical spine and intervertebral movement in normal adults. It will provide anatomic and movement parameters of the cervical spine for the design of artificial protheses.Methods: 1) One hundred and twenty adult volunteers (range 19-45 years) were selected to take cervical X-ray photos (lateral view) in neutral, flexing and extending position. Photos were excluded from the study if any cervical vertebrae were missing, obvious morphological abnormal and undergone surgical trauma or tumor which would render measurement inaccurate. This left a sample of 108 volunteers, 48 males (average 29.31, range 22-43 years), 60 females (average 32.20, range 19-45 years). Then, given computer-assisted measurement, the anterior, middle and posterior heights of vertebral bodies in neutral position; the anterior, middle and posterior heights of intervertebral disks in neutral, flexing and extending position. Calculate the difference of the heights of intervertebral disks between flexing position and extending position; Calculate the rate of intervertebral disk and vertebral body; Measure the intervertebral movement (C₂-C₇) beteen flexing position and extending position. Statistic analyses were carried out at the end; 2) Ten healthy adult volunteers (5 male and 5 female, average 29.31, range 22-43 years) underwent three-dimensional CT of the cervical spine(include neutral, right and left maximum rotation, right and left maximum bending ). Relative motion between occiput (Oc) and (T1) were measured using our self-designed software analysis system. Statistic analyses were carried out at the end.Results: 1) The heights of anterior and posterior part of vertebral body are higher than the middle part. There were significant differences between them P<0.05). There were significant differences between male and female in the height of vertebral body (P<0.05). The value of male group was higher than female group. There were significant differences between the sex and position in the heights of intervertebral disks (P<0.05). The value of male group is higher than female group. The height of middle part of the intervertebral disk is the highest, and anterior is the second, and posterior is the third. The difference of the height of intervertebral disks between flexing position and extending position in the anterior part is higher than the posterior part. There were significant differences between them (P<0.05). The rate of middle intervertebral disk and vertebral body is higher than anterior and posterior part. There were significant differences between them (P<0.05). There was no statistically significant difference (P<0.05) between male and female in the intervertebral (C₂-T₁) flexion-extension.; 2) Mean maximum axial rotation to one side at C₁-C₂ is greater than other levels. There are coupled lateral bending movements in the opposite direction as axial rotation at Co-C1 and C₁-C₂, and same direction at other levels. Extention coupled with axial rotation occurred in the upper and middle cervical region (Oc–C₅), while in the lower cervical spine (C₆–T₁), flexion was coupled with axial rotation. Slight lateral, anteroposterior and superoinferior translation coupled with axial rotation at the origin of coordinates was observed at all levels. Coupled axial rotation opposite to lateral bending was observed in the upper cervical levels, while the subaxial cervical levels except for C₇–T₁ displayed axial rotation in the same direction as lateral bending. Extention coupled with lateral bending occurred at Oc-C₁, while at other levels flexion was coupled with lateral bending. Similarly to axial rotation, slight lateral, anteroposterior and superoinferior translation coupled with lateral bending at the origin of coordinates was observed at all levels. Conclusions: 1) The heights of anterior and posterior part vertebral body are similar, but higher than the middle part. The height of middle part of the intervertebral disk is the highest, the anterior is the second and the posterior is the third. The physiological front prominence of the cervical spine is caused by the higher height of the anterior intervertebral disks. Therefore, in the process of design, elaboration and make use of artificial protheses, attention should be paid to this character. 2) The major movement of cervical spine is flexion and extension, especially sub-cervical spine. Therefore, in the process of design of artificial protheses, it is important to ensure enough movement of flexion and extension. 3) We have measured intervertebral coupled motions of the cervical spine in vivo successfully using three-dimensional CT image. It will help us further understanding the complicated motions of the cervical spine, and will provide an anatomic basis for the stability assessment of the cervical spine, the design of artificial protheses and the functional assessment after surgery.