Viano David C, Casson Ira R, Pellman Elliot J
ProBiomechanics LLC, Bloomfield Hills, Michigan 48304, USA.
Neurosurgery. 2007 Aug;61(2):313-27; discussion 327-8. doi: 10.1227/01.NEU.0000279969.02685.D0.
Impacts causing concussion in professional football were simulated in laboratory tests to determine collision mechanics. This study focuses on the biomechanics of concussion in the struck player.
Twenty-five helmet impacts were reconstructed using Hybrid III dummies. Head impact velocity, direction, and helmet kinematics-matched game video. Translational and rotational accelerations were measured in both players' heads; 6-axis upper neck responses were measured in all striking and five struck players. Head kinematics and biomechanics were determined for concussed players. Head displacement, rotation, and neck loads were determined because finite element analysis showed maximum strains occurring in the midbrain after the high impact forces. A model was developed of the helmet impact to study the influence of neck strength and other parameters on head responses.
The impact response of the concussed player's head includes peak accelerations of 94 +/- 28 g and 6432 +/- 1813 r/s2, and velocity changes of 7.2 +/- 1.8 m/s and 34.8 +/- 15.2 r/s. Near the end of impact (10 ms), head movement is only 20.2 +/- 6.8 mm and 6.9 +/- 2.5 degrees. After impact, there is rapid head displacement involving a fourfold increase to 87.6 +/- 21.2 mm and 29.9 +/- 9.5 degrees with neck tension and bending at 20 ms. Impacts to the front of the helmet, the source of the majority of National Football League concussions, cause rotation primarily around the z axis (superior-inferior axis) because the force is forward of the neck centerline. This twists the head to the right or left an average of 17.6 +/- 12.7 degrees, causing a moment of 17.7 +/- 3.3 Nm and neck tension of 1704 +/- 432 N at 20 ms. The head injury criterion correlates with concussion risk and is proportional to deltaV(4)/d(1.5) for half-sine acceleration. Stronger necks reduce head acceleration, deltaV, and displacement. Even relatively small reductions in deltaV have a large effect on head injury criterion that may reduce concussion risks because changes in deltaV change head injury criterion through the 4th power.
This study addresses head responses causing concussion in National Football League players. Although efforts are underway to reduce impact acceleration through helmet padding, further study is needed of head kinematics after impact and their contribution to concussion, including rapid head displacement, z-axis rotation, and neck tension up to the time of maximum strain in the midbrain. Neck strength influences head deltaV and head injury criterion and may help explain different concussion risks in professional and youth athletes, women, and children.
在实验室测试中模拟职业橄榄球运动中导致脑震荡的撞击，以确定碰撞力学原理。本研究聚焦于被撞击球员脑震荡的生物力学。
使用混合III型人体模型重建了25次头盔撞击。头部撞击速度、方向以及头盔运动学与比赛视频相匹配。测量了双方球员头部的平移和旋转加速度；在所有撞击球员以及五名被撞击球员中测量了6轴上颈部响应。确定了脑震荡球员的头部运动学和生物力学。确定了头部位移、旋转和颈部负荷，因为有限元分析表明在高冲击力作用后中脑会出现最大应变。开发了一个头盔撞击模型，以研究颈部力量和其他参数对头部响应的影响。
脑震荡球员头部的撞击响应包括峰值加速度为94±28g和6432±1813r/s²，速度变化为7.2±1.8m/s和34.8±15.2r/s。在撞击接近尾声时（10毫秒），头部移动仅为20.2±6.8毫米和6.9±2.5度。撞击后，头部会迅速位移，在20毫秒时颈部张力和弯曲导致头部位移增加四倍，达到87.6±21.2毫米和29.9±9.5度。头盔前部受到的撞击是美国国家橄榄球联盟中大多数脑震荡的起因，由于力作用于颈部中心线前方，主要导致头部绕z轴（上下轴）旋转。这会使头部左右平均扭转17.6±12.7度，在20毫秒时产生17.7±3.3牛米的力矩和1704±432牛的颈部张力。头部损伤标准与脑震荡风险相关，对于半正弦加速度而言，与ΔV(4)/d(1.5)成正比。更强壮的颈部会降低头部加速度、ΔV和位移。即使ΔV相对较小的降低也会对头部损伤标准产生很大影响，这可能会降低脑震荡风险，因为ΔV的变化会通过四次方改变头部损伤标准。
本研究探讨了美国国家橄榄球联盟球员中导致脑震荡的头部响应。尽管正在努力通过头盔衬垫来降低撞击加速度，但仍需要进一步研究撞击后头部的运动学及其对脑震荡的影响，包括快速头部位移、z轴旋转以及直至中脑出现最大应变时的颈部张力。颈部力量会影响头部的ΔV和头部损伤标准，这可能有助于解释职业运动员与青少年运动员、女性和儿童中不同的脑震荡风险。
