跟骨三维有限元模型的建立与静态分析

目的 建立一个基于健康人体的跟骨三维有限元模型,静态分析双足站立相时跟骨内部的生物力学特性,探讨跟骨骨折疼痛的内外侧应力不均衡因素.方法 选取1名健康男性志愿者,年龄28岁,体重64kg.采用16排螺旋CT对足部沿横断面连续扫描,将符合DICOM 3.0标准的CT断层图像导入MIMICS10.1中,设定阈值为226～3071 Houfield unit,确定方位后经手动编辑、区域增长、形态学操作及空洞处理等,生成足部的三维模型,从整个足部模型中提取跟骨模型.对跟骨进行面网格的优化处理后,导入ANSYS10.0中得到体网格模型.根据CT断层图像的灰度值完成模型材质的添加,生成最终的三维有限元模型.模拟研究对象双足静止站立的状态,距下关节面在整个分析过程中被全约束,自足跟及跟腱附着点处对模型分别施加垂直向上的320 N和160 N载荷,观察跟骨的Vonmises应力分布.结果 MIMICS软件能够迅速建立更为精确的有限元模型,当垂直载荷作用于跟骨后,跟骨内、外侧存在一定的应力不均衡因素.跟骨的外侧结构是明显的薄弱区域,随着跟骨外侧壁的应力增加,导致继发外侧畸形,压迫腓骨长短肌及跟骰关节产生疼痛.结论 创建的跟骨三维有限元模型,经验证是一个较为精确的正常跟骨三维模型,可用于理解跟骨内部的应力分布变化.

Foundation and static analysis of calcaneal three-dimensional finite element model

Objective To establish a more rapid and precise calcaneal three-dimensional (3D) finite element model based on the healthy human foot, to analyze the internal biomechanical properties of calcaneus, and to explore the relationship between caleaneal fracture pain with the stress imbalance factors in medial and lateral side of calcaneus. Methods One healthy male volunteer (28 years old, 64 kg) was selected. Input DICOM 3.0 standard CT sectional images into MIMICS10.1 software, set the threshold of 226-3071 Houfield unit, generate foot 3D model, extract caleaneus, optimize it into surface mesh model, and use ANSYS10.0 to develop grid mesh. According to CT sectional images of the gray value, the model materials were added, and the final 3D finite element model of ealeaneus was generated. The static standing posture was simulates using the static finite element analysis. Subtalar joint surface in the whole analysis process was fully constrained during the study period. The forces of 320 N and 160 N were loaded in perpendicular direction on heel and attachment point of Achilles tendon respectively to detect the Vonmises stress distribution of the calcaneus. Results MIMICS software can quickly establish a more accurate finite element model. When the vertical load acting on the calcaneus, there is a clear imbalance of factors about the calcaneal lateral and medial stress. The lateral calcaneal structure is a clearly weak area. The increased stress applied on the lateral wall of calcaneus, lead to secondary lateral deformity, which pressed the long and short muscle tendon of fibula and calcaneocubeid articulation, and generated pain. Conclusion The calcaneal finite element model is proved to be a correct and reliable model, which can help to understand the stress dispersion of calcaneal inner part.