PDF(Pubmed)
Abstract：
UNASSIGNED: Facet fractures are frequently associated with clinically observed cervical facet dislocations (CFDs); however, to date there has only been one experimental study, using functional spinal units (FSUs), which has systematically produced CFD with concomitant facet fracture. The role of axial compression and distraction on the mechanical response of the cervical facets under intervertebral motions associated with CFD in FSUs has previously been shown. The same has not been demonstrated in multi-segment lower cervical spine specimens under flexion loading (postulated to be the local injury vector associated with CFD).
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.
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.
摘要：
■关节突骨折通常与临床观察到的颈椎关节脱位（CFDs）相关；然而，迄今为止，只有一项实验研究，使用功能性脊柱单位（FSU），系统地产生了伴随小平面骨折的CFD。先前已经显示了轴向压缩和牵引在与FSU中的CFD相关的椎间运动下对颈椎小平面的机械响应的作用。在屈曲载荷下的下颈椎多节段标本中未证明相同（假定为与CFD相关的局部损伤矢量）。
■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。
■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。
