Lewin Susanne, Åberg Jonas, Neuhaus Dominique, Engqvist Håkan, Ferguson Stephen J, Öhman-Mägi Caroline, Helgason Benedikt, Persson Cecilia
Div. of Applied Materials Science, Dept. of Engineering Sciences, Uppsala University, Uppsala, Sweden.
Div. of Applied Materials Science, Dept. of Engineering Sciences, Uppsala University, Uppsala, Sweden.
J Mech Behav Biomed Mater. 2020 Apr;104:103701. doi: 10.1016/j.jmbbm.2020.103701. Epub 2020 Feb 15.
Cranial implants are used to repair bone defects following neurosurgery or trauma. At present, there is a lack of data on their mechanical response, particularly in impact loading. The aim of the present study was to assess the mechanical response of a recently developed composite calcium phosphate-titanium (CaP-Ti) implant at quasi-static and impact loading rates. Two different designs were tested, referred to as Design 1 (D1) and Design 2 (D2). The titanium structures in the implant specimens were additively manufactured by a powder-bed fusion process and subsequently embedded in a self-setting CaP material. D1 was conceptually representative of the clinically used implants. In D2, the titanium structure was simplified in terms of geometry in order to facilitate the manufacturing. The mechanical response of the implants was evaluated in quasi-static compression, and in impact using a drop-tower. Similar peak loads were obtained for the two designs, at the two loading rates: 808 ± 29 N and 852 ± 34 for D1, and 840 ± 40 N and 814 ± 13 for D2. A strain rate dependency was demonstrated for both designs, with a higher stiffness in the impact test. Furthermore, the titanium in the implant fractured in the quasi-static test (to failure) but not in the impact test (to 5.75 J) for D1. For D2, the displacement at peak load was significantly lower in the impact test than in the quasi-static test. The main difference between the designs was seen in the quasi-static test results where the deformation zones, i.e. notches in the titanium structure between the CaP tiles, in D1 likely resulted in a localization of the deformation, compared to in D2 (which did not have deformation zones). In the impact test, the only significant difference between the designs was a higher maximum displacement of D2 than of D1. In comparison with other reported mechanical tests on osteoconductive ceramic-based cranial implants, the CaP-Ti implant demonstrates the highest reported strength in quasi-static compression. In conclusion, the titanium structure seems to make the CaP-Ti implant capable of cerebral protection in impact situations like the one tested in this study.
颅骨植入物用于修复神经外科手术或创伤后的骨缺损。目前，关于其力学响应的数据匮乏，尤其是在冲击载荷方面。本研究的目的是评估一种新开发的磷酸钙 - 钛（CaP - Ti）复合植入物在准静态和冲击加载速率下的力学响应。测试了两种不同的设计，分别称为设计1（D1）和设计2（D2）。植入物标本中的钛结构通过粉末床熔融工艺增材制造，随后嵌入自固化CaP材料中。D1在概念上代表临床使用的植入物。在D2中，钛结构在几何形状上进行了简化以利于制造。通过准静态压缩和落塔冲击试验评估植入物的力学响应。在两种加载速率下，两种设计获得了相似的峰值载荷：D1为808±29 N和852±34 N，D2为840±40 N和814±13 N。两种设计均表现出应变率依赖性，冲击试验中的刚度更高。此外，对于D1，植入物中的钛在准静态试验（直至失效）中发生断裂，但在冲击试验（至5.75 J）中未断裂。对于D2，冲击试验中峰值载荷时的位移明显低于准静态试验。两种设计之间的主要差异出现在准静态试验结果中，与D2（没有变形区）相比，D1中CaP块之间钛结构中的变形区（即缺口）可能导致变形局部化。在冲击试验中，两种设计之间唯一显著的差异是D2的最大位移高于D1。与其他报道的关于骨传导性陶瓷基颅骨植入物的力学测试相比，CaP - Ti植入物在准静态压缩中表现出最高的报道强度。总之，钛结构似乎使CaP - Ti植入物能够在本研究测试的冲击情况下起到脑保护作用。
