Cirovic S, Bhola R M, Hose D R, Howard I C, Lawford P V, Parsons M A
Department of Mechanical Engineering, the University of Sheffield, Sheffield, UK.
Forensic Sci Med Pathol. 2005 Mar;1(1):53-9. doi: 10.1385/FSMP:1:1:053.
The terms abusive head injury and shaken baby syndrome are used to describe a unique pattern of nonaccidental traumatic injuries occurring in children that many clinicians and researchers have good reason to believe is caused by violent shaking. Typical injuries include severe brain injury, with intracranial and retinal hemorrhages, but the pathogenesis of injuries is poorly understood. A major paradox in head trauma in infants is that the injuries induced by a shaking event are much more severe than those caused by even very violent single-impact head trauma, despite the relatively low accelerations in shaking.We have developed a finite element computer model of the eye, orbit, and orbital bone and used it to simulate the effects of single-impact and oscillatory motion inputs. The model was informed by data from semiquantitative in vitro anatomical traction experiments on in situ rabbit eyes. The new results reported here strongly suggest that suction between the eye and its surrounding fat dominates the dynamical stability of the system composed of the eye, its socket, and the components and material supporting the eye. Computer simulations incorporating this functional anatomical relationship show that deceleration of the head generates pressure gradients inside and outside the eye; these could cause damaging shear stresses in structures such as the retina and blood vessels. Simulations also show that oscillating the bone of the orbit causes the eye to move anteriorly and posteriorly with an increasing amplitude, building up the stresses within the eye over time. This is the first time that any biomechanical mechanism has been identified that might explain the disproportionally severe injuries caused by an oscillatory mechanism such as violent shaking of an abused infant. However, further study is required and this conclusion is therefore preliminary and provisional.
虐待性头部损伤和摇晃婴儿综合征这两个术语用于描述儿童非意外性创伤损伤的一种独特模式，许多临床医生和研究人员有充分理由认为这是由剧烈摇晃所致。典型损伤包括严重脑损伤以及颅内和视网膜出血，但损伤的发病机制尚不清楚。婴儿头部创伤的一个主要矛盾之处在于，尽管摇晃时的加速度相对较低，但摇晃事件导致的损伤比即使非常剧烈的单次撞击头部创伤所造成的损伤要严重得多。我们开发了一个眼睛、眼眶和眶骨的有限元计算机模型，并利用它来模拟单次撞击和振荡运动输入的影响。该模型依据对原位兔眼进行的半定量体外解剖牵引实验数据构建。此处报告的新结果有力地表明，眼睛与其周围脂肪之间的吸力主导着由眼睛、眼窝以及支撑眼睛的部件和材料组成的系统的动态稳定性。纳入这种功能解剖关系的计算机模拟表明，头部减速会在眼内和眼外产生压力梯度；这些压力梯度可能会在视网膜和血管等结构中引起破坏性的剪切应力。模拟还表明，眼眶骨的振荡会使眼睛前后移动，且振幅不断增大，随着时间的推移在眼内积聚应力。这是首次确定任何可能解释诸如虐待婴儿时剧烈摇晃这种振荡机制所导致的不成比例的严重损伤的生物力学机制。然而，仍需进一步研究，因此这一结论是初步的、临时的。
