颈椎曲度

人出生后就存在颈椎前凸，三抬、四翻、六坐、七滚、八爬、九立、周会走。这样三月份后，颈椎前凸逐渐增加，坐起和站立维持头颅的位置，一直增加到2岁左右，2-9岁期间前凸逐渐降低，9-18岁期间前凸有逐渐增加。

成年后颈椎曲度可以分为四种类型（类似于腰椎曲度，成人后颈椎曲度也不能用单一的前凸角度来评估，腰椎前凸是和骨盆PI相对应，而颈椎前凸应该和胸廓相匹配）。

Toyama分型：lordotic type, straight type, sigmoid type, and kyphotic type（根据各C3 ~ C6椎体中心到C2下终板中点与C7上终板中点连线的垂直距离）

Donk分型：lordotic type, straight type and kyphotic type（根据C3 ~ C6椎体后缘与C2椎体后下缘和C7椎体后上缘连线的相对位置）

Virk分型：large lordosis cohort, small lordosis cohort, and kyphotic cohort（C2-7CL和T1 Slop）

华山分型：(A) large lordosis. (B) Small lordosis. (C) straight. (D) Kyphosis.

（从高T1-Slop到低T1-Slop）类似腰椎（Roussouly分型中、腰椎下腰弯和SS相等，上腰弯固定在20度），颈椎是（C4以上上颈椎角度比较固定，曲度不同主要在下颈椎）

Large lordosis (LL): CL ≥ -1.5×T1 slope (TS)+70°；Small lordosis (SL): -1.5×TS+50° ≤ CL < -1.5×TS+70°;Straight (S): 0° ≤ CL < -1.5×TS+50°；K: CL < 0°；  高TS对应高CL。

按照roussouly分形，高TS也来自高PI

退变后，退变因素（前方高度丢失、后方肌肉力量降低）导致前凸减小；代偿因素（胸椎后凸增加后，为了直视）导致前凸增加。

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2.Gong Z, Xu H, Yang Y, et al. A Novel Cervical Sagittal Classification for Asymptomatic Population Based on Cluster Analysis. Clinical Spine Surgery. Epub ahead of print April 10, 2024. DOI: 10.1097/BSD.0000000000001629.

3.Virk S, Lafage R, Elysee J, et al. The 3 Sagittal Morphotypes That Define the Normal Cervical Spine: A Systematic Review of the Literature and an Analysis of Asymptomatic Volunteers. Journal of Bone and Joint Surgery 2020;102:e109.

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7.Kasai T, Ikata T, Katoh S, et al. Growth of the cervical spine with special reference to its lordosis and mobility. Spine (Phila Pa 1976) 1996;21:2067–73.