Changes of cervical sagittal alignments during motions in patients with cervical kyphosis

Abstract

Changes of cervical sagittal alignment during motion in cervical kyphosis patients have never been published before. This study was to investigate the changes and provide a better reference for orthopedic treatment.Randomized double-blind repeat trial was carried out on 60 patients with cervical kyphosis. On standard position, hyper flexion, and hyper extension sagittal radiographs, the following measurements were made: the C2-7 vertebral body spatial alignment angle (∠A), C2-7 vertebral lower terminal lamina tilt angle (∠B), C2/3 to C6/7 segmental intervertebral space angle (∠C), the distance from the posterior edge of odontoid to C7 vertebral body (D value), and the difference of angle A, B, and C between cervical flexion and extension movement. Another 60 healthy volunteers were enrolled, of whom the cervical curve apex was determined using Borden's method to compare change and distribution characteristics to patients with cervical kyphosis and C value.In standard lateral position, ∠A was positive and increased from C2 to C7. In hyper extension position, ∠A decreased with reducing amplitude from C2 to C7 compared with the standard position, whereas in hyper flexion position, the average value of ∠A increased with decreasing amplitude from C2 to C7. ∠B followed similar change regularities as ∠A with a larger mean value. In cervical flexion and extension movement, ∠A change of upper vertebral body (∠D) was almost equal to ∠A change of lower vertebral body and ∠C change between the adjacent 2 vertebral bodies (∠E). The curve apex distribution was almost between C4 and C5 in cervical kyphosis patients. A significant difference was observed between cervical kyphosis patients and normal people in C value and D value.The correction of the cervical kyphosis can be carried out from the apex of the cervical spine that provides a solid theoretical foundation for the correction of the cervical kyphosis.

Figure 1

∠A, the angle between the line connecting the midpoints of vertebral posterior and anterior edge and the line parallel to the radiograph baseline level. ∠B, the angle between the inferior endplate line and the line parallel to the radiographic baseline. ∠C the angle between the lines connecting superior and inferior vertebral endplates within the same intervertebral space segment. C value, a perpendicular line is drawn from the widest gap point between lines A and B. D value (the distance between the posterior of odontoid process to posterior of C7 vertebrae), ∠F, the angle between the posterior of 2 adjacent vertebral bodies.

Figure 2

In standard position, each vertebral body spatial alignment ∠A average is positive that increases from C2 to C7. In the hyper extension position, the mean value of ∠A decreases compared with the standard position, and the reduction amplitude decreases from C2 to C7. The average value of the 2 is basically the same in C7 vertebral body. Overall, the average value of ∠A increases from C2 to C7 gradually the same as the standard position, just average C2 value is negative. In the hyper flexion position, the average value of ∠A increases compared with the standard position, and the increased amplitude decreases from C2 to C7. The average value of the 2 is basically the same in C7 vertebral body. The difference is that the average value of ∠A decreases from C2 to C7. ∠B follows similar change regularities as ∠A with a larger mean value than ∠A.

Figure 3

The change of ∠A (the ∠A difference between hyper flexion and hyper extension) decreases from C2 to C7. The change of ∠B (the ∠B difference between hyper flexion and hyper extension) follows the same change trend.

Figure 4

In the cervical flexion and extension movements, ∠A change of upper vertebral body (∠D) is almost equal to ∠A change of lower vertebral body and ∠C change between the 2 vertebrae bodies.(∠E).

Figure 5

In the standard position, the cervical curve apex distribution is almost between C4 (42%) and C5 (44%).This is basically the same with normal people.