Department of Mechanical Engineering, College of Engineering, Nihon University, 1 Nakagawara, Tokusada, Tamuramachi, Koriyama, 963-8642, Japan.
Department of Mechanical System Engineering, Nagoya University, Furo-Cho, Chikusa-Ku, Nagoya, 464-8603, Japan.
Biomed Eng Online. 2024 Sep 11;23(1):94. doi: 10.1186/s12938-024-01284-2.
The thresholds of mechanical inputs for bruising caused by blunt impact are important in the fields of machine safety and forensics. However, reliable data on these thresholds remain inadequate owing to a lack of in vivo experiments, which are crucial for investigating the occurrence of bruising. Since experiments involving live human participants are limited owing to ethical concerns, finite-element method (FEM) simulations of the bruising mechanism should be used to compensate for the lack of experimental data by estimating the thresholds under various conditions, which requires clarifying the mechanism of formation of actual bruises. Therefore, this study aimed to visualize the mechanism underlying the formation of bruises caused by blunt impact to enable FEM simulations to estimate the thresholds of mechanical inputs for bruising.
In vivo microscopy of a transparent glass catfish subjected to blunt contact with an indenter was performed. The fish were anesthetized by immersing them in buffered MS-222 (75-100 mg/L) and then fixed on a subject tray. The indenter, made of transparent acrylic and having a rectangular contact area with dimensions of 1.0 mm × 1.5 mm, was loaded onto the lateral side of the caudal region of the fish. Blood vessels and surrounding tissues were examined through the transparent indenter using a microscope equipped with a video camera. The contact force was measured using a force-sensing table.
One of the processes of rupturing thin blood vessels, which are an essential component of the bruising mechanism, was observed and recorded as a movie. The soft tissue surrounding the thin blood vessel extended in a plane perpendicular to the compressive contact force. Subsequently, the thin blood vessel was pulled into a straight configuration. Next, it was stretched in the axial direction and finally ruptured.
The results obtained indicate that the extension of the surrounding tissue in the direction perpendicular to the contact force as well as the extension of the thin blood vessels are important factors in the bruising mechanism, which must be reproduced by FEM simulation to estimate the thresholds.
钝器冲击引起瘀伤的机械输入阈值在机器安全和法医学领域很重要。然而，由于缺乏活体实验，这些阈值的可靠数据仍然不足，因为活体实验对于研究瘀伤的发生至关重要。由于涉及活体人类参与者的实验受到伦理问题的限制，因此应该使用有限元方法（FEM）模拟瘀伤机制，通过在各种条件下估计阈值来弥补实验数据的不足，这需要澄清实际瘀伤形成的机制。因此，本研究旨在可视化钝器冲击引起瘀伤的形成机制，以使 FEM 模拟能够估计瘀伤机械输入阈值。
对透明玻璃猫鱼进行体内显微镜检查，使其与压头发生钝性接触。将鱼浸入缓冲 MS-222（75-100mg/L）中麻醉，然后固定在受试托盘上。压头由透明亚克力制成，具有 1.0mm×1.5mm 的矩形接触面，加载到鱼尾部的侧面。通过配备摄像头的显微镜检查透明压头下的血管和周围组织。使用力感测台测量接触力。
观察并记录了作为电影的一个破裂细血管的过程，这是瘀伤机制的一个重要组成部分。薄血管周围的软组织在垂直于压缩接触力的平面上延伸。随后，薄血管被拉成直线配置。接下来，它在轴向方向上被拉伸，最后破裂。
结果表明，周围组织在垂直于接触力的方向上的延伸以及细血管的延伸是瘀伤机制中的重要因素，这必须通过 FEM 模拟来重现，以估计阈值。
