Chen Siyuan, Kleiven Svein, Li Xiaogai
Division of Neuronic Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
Biomech Model Mechanobiol. 2025 Feb;24(1):153-168. doi: 10.1007/s10237-024-01902-x. Epub 2024 Nov 25.
The geometry and mechanical properties of infant skull bones differ significantly from those of adults. Over the past decades, debates surrounding whether fractures in infants come from deliberate abuse or accidents have generated significant impacts in both legal and societal contexts. However, the etiology of infant skull fractures remains unclear, which motivates this study with two main components of work. Firstly, we present and implement a progressive unidirectional fabric composite damage model for infant cranial vaults to represent ductile and anisotropic properties-two typical mechanical characteristics of infant skulls. Secondly, we hypothesize that these intrinsic material properties cause injuries perpendicular to the fiber direction to dominate infant skull fractures, resulting in fracture lines that align with the direction of mineralization in the infant skull. The material model and the finite element (FE) model were verified hierarchically, and this hypothesis was verified by reconstructing two legal cases with known fall heights and implementing the above damage model into CT-based subject-specific infant FE head models. We discovered that the infant skull is more susceptible to injuries within planes perpendicular to the mineralization direction because of the anisotropic mechanical property caused by the direction of mineralization, leading to infant skull fractures aligning with the mineralization direction. Our findings corroborated the several previously reported observations of fractures on cranial vaults, demonstrating that these fractures were closely associated with sutures and oriented along the mineralization direction, and revealed the underlying mechanisms of infant skull fracture pattern. The modeling methods and results of this study will serve as an anchor point for more rigorous investigations of infant skull fractures, ultimately aiming to provide convincing biomechanical evidence to aid forensic diagnoses of abusive head trauma.
婴儿颅骨的几何形状和力学性能与成人有显著差异。在过去几十年里，围绕婴儿骨折是源于故意虐待还是意外事故的争论在法律和社会背景下都产生了重大影响。然而，婴儿颅骨骨折的病因仍不明确，这促使本研究开展了两个主要工作内容。首先，我们提出并实施了一种用于婴儿颅顶的渐进单向织物复合材料损伤模型，以表征婴儿颅骨的韧性和各向异性特性——这是婴儿颅骨的两个典型力学特征。其次，我们假设这些内在材料特性导致垂直于纤维方向的损伤在婴儿颅骨骨折中占主导地位，从而产生与婴儿颅骨矿化方向一致的骨折线。对材料模型和有限元（FE）模型进行了分层验证，并通过重建两起已知坠落高度的法律案件并将上述损伤模型应用于基于CT的特定婴儿有限元头部模型来验证这一假设。我们发现，由于矿化方向导致的各向异性力学性能，婴儿颅骨在垂直于矿化方向的平面内更容易受伤，从而导致婴儿颅骨骨折与矿化方向一致。我们的研究结果证实了先前关于颅顶骨折的几项观察结果，表明这些骨折与缝合线密切相关且沿矿化方向排列，并揭示了婴儿颅骨骨折模式的潜在机制。本研究的建模方法和结果将为更严格地研究婴儿颅骨骨折提供一个支撑点，最终旨在提供有说服力的生物力学证据，以协助法医诊断虐待性头部创伤。
