UNASSIGNED: This study investigated the mechanical response of the bilateral inferior C6 facets of thirteen C5-C7 specimens (67±13 yr, 6 male) during non-destructive constrained flexion, superimposed with each of five axial conditions: (1) 50 N compression (simulating weight of the head); (2-4) 300, 500, and 1000 N compression (simulating the spectrum of intervertebral compression resulting from neck muscle bracing prior to head-first impact and/or externally applied compressive forces); and, (5) 2 mm of C6/C7 distraction (simulating the intervertebral distraction present during inertial loading of the cervical spine by the weight of the head). Linear mixed-effects models (α = 0.05) assessed the effect of axial condition.
UNASSIGNED: Increasing amounts of intervertebral compression superimposed on flexion rotations, resulted in increased facet surface strains (range of estimated mean difference relative to Neutral: maximum principal = 77 to 110 με, minimum principal = 126 to 293 με, maximum shear = 203 to 375 με) and angular deflection of the bilateral inferior C6 facets relative to the C6 vertebral body (range of estimated mean difference relative to Neutral = 0.59° to 1.47°).
UNASSIGNED: These findings suggest increased facet engagement and higher load transfer through the facet joint, and potentially a higher likelihood of facet fracture under the compressed axial conditions.
■本研究调查了13个C5-C7标本(67±13年,6男性)在非破坏性约束屈曲期间,与五个轴向条件中的每一个叠加:(1)50N压缩(模拟头部的重量);(2-4)300、500和1000N压缩(模拟在头部第一冲击和/或外部施加的压缩力之前由颈部肌肉支撑产生的椎间压缩的频谱);和,(5)2mm的C6/C7牵张(模拟在颈椎因头部重量而惯性加载期间存在的椎间牵张)。线性混合效应模型(α=0.05)评估了轴向条件的影响。
■增加的椎间压缩叠加在屈曲旋转上,导致小平面表面应变增加(相对于中性的估计平均差范围:最大主=77至110με,最小主=126至293με,最大剪切=203至375με)和双侧下C6小平面相对于C6椎体的角偏转(相对于中性的估计平均差范围=0.59°至1.47°)。
■这些发现表明,通过小平面关节增加了小平面接合和更高的载荷传递,在压缩轴向条件下,小面断裂的可能性更高。