Lewin Susanne, Fleps Ingmar, Neuhaus Dominique, Öhman-Mägi Caroline, Ferguson Stephen J, Persson Cecilia, Helgason Benedikt
Department of Materials Science and Engineering, Uppsala University, Uppsala, Sweden.
Institute for Biomechanics, ETH Zurich, Zurich, Switzerland.
J Mech Behav Biomed Mater. 2020 Dec;112:104085. doi: 10.1016/j.jmbbm.2020.104085. Epub 2020 Sep 20.
The structural integrity of cranial implants is of great clinical importance, as they aim to provide cerebral protection after neurosurgery or trauma. With the increased use of patient-specific implants, the mechanical response of each implant cannot be characterized experimentally in a practical way. However, computational models provide an excellent possibility for efficiently predicting the mechanical response of patient-specific implants. This study developed finite element models (FEMs) of titanium-reinforced calcium phosphate (CaP-Ti) implants. The models were validated with previously obtained experimental data for two different CaP-Ti implant designs (D1 and D2), in which generically shaped implant specimens were loaded in compression at either quasi-static (1 mm/min) or impact (5 kg, 1.52 m/s) loading rates. The FEMs showed agreement with experimental data in the force-displacement response for both implant designs. The implicit FEMs predicted the peak load with an underestimation for D1 (9%) and an overestimation for D2 (11%). Furthermore, the shape of the force-displacement curves were well predicted. In the explicit FEMs, the first part of the force-displacement response showed 5% difference for D1 and 2% difference for D2, with respect to the experimentally derived peak loads. The explicit FEMs efficiently predicted the maximum displacements with 1% and 4% difference for D1 and D2, respectively. Compared to the CaP-Ti implant, an average parietal cranial bone FEM showed a stiffer response, greater energy absorption and less deformation under the same impact conditions. The framework developed for modelling the CaP-Ti implants has a potential for modelling CaP materials in other composite implants in future studies since it only used literature based input and matched boundary conditions. Furthermore, the developed FEMs make an important contribution to future evaluations of patient-specific CaP-Ti cranial implant designs in various loading scenarios.
颅骨植入物的结构完整性具有重要的临床意义，因为其目的是在神经外科手术或创伤后提供脑部保护。随着定制植入物使用的增加，以实际可行的方式通过实验来表征每个植入物的力学响应是不可能的。然而，计算模型为有效预测定制植入物的力学响应提供了绝佳的可能性。本研究开发了钛增强磷酸钙（CaP-Ti）植入物的有限元模型（FEM）。这些模型用先前获得的两种不同CaP-Ti植入物设计（D1和D2）的实验数据进行了验证，其中一般形状的植入物标本在准静态（1毫米/分钟）或冲击（5千克，1.52米/秒）加载速率下进行压缩加载。FEM在两种植入物设计的力-位移响应方面均与实验数据相符。隐式FEM预测的峰值载荷对于D1低估了9%，对于D2高估了11%。此外，力-位移曲线的形状得到了很好的预测。在显式FEM中，力-位移响应的第一部分与实验得出的峰值载荷相比，D1有5%的差异，D2有2%的差异。显式FEM分别以1%和4%的差异有效预测了D1和D2的最大位移。与CaP-Ti植入物相比，平均顶骨颅骨有限元模型在相同冲击条件下表现出更硬的响应、更大的能量吸收和更小的变形。为CaP-Ti植入物建模开发的框架在未来研究中具有对其他复合植入物中的CaP材料进行建模的潜力，因为它仅使用基于文献的输入和匹配的边界条件。此外，所开发的FEM对未来在各种加载场景下对定制CaP-Ti颅骨植入物设计的评估做出了重要贡献。
