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

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.