• Zhou Xu-hui, Fang Jia-hu, Jia Lian-shun, Chi Zhi-yong, Zhang Yong, Chen Xiong-sheng, and Wan Wei-ping.
• Department of Orthopedics, Shanghai Changzheng Hospital, 415 Fengyang Road, Shanghai, People's Republic of China.
• Spine. 2009 Jan 1;34(1):E21-6.

Study DesignRadiographic review.ObjectiveTo study changes in alignment and curvature of the cervical vertebral column in the sagittal plane, and to provide references for the orthopedic treatment of cervical kyphosis.Summary And Background DataThere are few reports analyzing changes of the vertebral body itself or changes in their relationships between separate vertebrae. To understand cervical vertebrae and curvature dynamic variation patterns in the sagittal plane and provide a theoretical reference for orthopedic correction of cervical kyphosis, we measured spatial position and alignment of the cervical vertebrae on sagittal plane films of various postures.MethodBlind repeated measures design analysis of sagittal view standard lateral, hyper flexion, and hyper extension cervical spine of 60 healthy subjects measuring spatial alignment angle of C2 to C7 vertebral bodies in the sagittal plain ( angleA), C2 to C7 inferior terminal lamina tilt angle of ( angleB), and segmental intervertebral space angles C2/3 to C6/7 ( angleC) calculating flexion and extension amplitude changes in angleA, angleB, and angleC. Cervical curve apex was determined using Borden's method to compare change and distribution characteristics. RESULTS.: Segmental angleA is a positive mean value that increases from C2 to C7 when in the upright position. In hyper extension, mean angleA value decreases with gradual amplitude decrease from C2 to C7; however, a gradual overall increasing pattern is observed for mean angleA from C2 to C7. In hyper flexion, segmental angleA mean value increases with gradual amplitude decrease from C2 to C7, whereas with decreasing angular measurements from C2 to C7. angleB follows similar change regularities as angleA with a larger mean value than angleA. During maximum extension and maximum flexion, angleD is equal to angleE. For example: C2 angleD = C2 variable angleA; C2 angleE angle(C3 variable angleA + C2/3 variable angleC); and C2 angleD = C2 angleE. Cervical spine curve apex is mainly distributed between C4 and C5 on standard, hyper extension and hyper flexion lateral view.ConclusionDynamic cervical curvature changes based on a central apex, stems from vertebral rotation and displacement in the sagittal plane. Our study reveals variation patterns of dynamic cervical spine sagittal alignment and curvature, providing vertebral spatial alignment value as reference for orthopedic cervical kyphosis corrective surgery.

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