Biomechanical analysis of different mineral bone substitutes for application in tibial head bone defects

胫骨头骨折占老年人所有骨折的10%。由于干骺端骨质流失，凹陷性骨折，特别是胫骨外侧平台的凹陷性骨折，经常发生，需要手术治疗。在复位凹陷的关节骨折碎片后，干骺端骨缺损仍然存在。由于嵴骨的脂肪变性，用自体嵴骨移植物填充缺损是不可能的。取而代之的是使用骨替代品。为了在最大载荷下提供足够的稳定性，同时防止继发性复位丢失，需要将骨替代物和接骨术相结合。磷酸钙骨水泥通常用作骨替代物，在轴向载荷下提供高稳定性，尽管它们没有可钻孔特性。在磷酸钙和磷酸镁基础上具有或不具有纤维增强的新型双固化矿物水泥是有前途的新骨替代物开发。特别是磷酸镁水泥，在短凝固时间后提供高稳定性，并且比磷酸钙水泥更好地控制其流变质量。这项拨款申请旨在比较这些新矿物水泥相对于标准磷酸钙水泥的生物力学性能，在水泥优化之前和之后。使用轴向载荷和三点弯曲测试，将首先表征骨替代物的生物力学特性。在合成骨中模拟胫骨头骨折后，将使用不同的骨水泥单独填充和与螺钉接骨术组合填充所产生的胫骨缺损，然后进行生物力学测试。然后通过修改聚乳酸-羟基乙酸共聚物（PLGA）纤维、纤维长度和甲基丙烯酸2-羟乙酯（HEMA）浓度来优化新矿物水泥的特性。然后，将优化的矿物骨水泥作为胫骨头骨折的骨替代物与不同的骨接合结合进行生物力学测试，并将其与标准磷酸钙骨水泥进行比较。这将涉及使用循环载荷方案对样本进行系统性载荷，以模拟与术后部分负重相关的较低载荷，并采用最大载荷方案（Zwick Roell Z 020，乌尔姆，德国）。最有前途的骨替代物和骨接合组合将在人体bones.The主要假设，这项研究的改性磷酸镁水泥（双固化和纤维增强）结合骨接合将显示出优越的生物力学性能相比，标准的磷酸钙水泥上级。

Tibial head fractures account for 10% of all fractures in the elderly. Due to metaphyseal bone loss, depression fractures, especially of the lateral tibial plateau, frequently occur and need to be treated operatively. After reduction of the depressed articular fracture fragment, a metaphyseal bone defect remains. Filling the defect with an autologous crest bone graft is not possible because of fatty degeneration of the crest bone. Instead, bone substitutes are used. To provide enough stability under maximal loading while preventing a secondary loss of reduction, a combination of bone substitute and osteosynthesis is needed. Calcium phosphate cements are usually used as bone substitutes, providing high stability under axial loading, although they have no drillable characteristics. New dual-setting mineral cements with or without fibre-reinforcement on a calcium phosphate and magnesium phosphate base are promising new bone substitute developments. Magnesium phosphate cements, in particular, provide high stability after a short setting time and are better to control in their rheological qualities than calcium phosphate cements. This grant application aims to compare the biomechanical properties of these new mineral cements relative to standard calcium phosphate cements, before and after the cements have been optimized. Using axial loading and 3-point-bending tests, the biomechanical properties of the bone substitutes will firstly be characterized. After simulating tibial head fractures in synthetic bones, the different cements will be used to fill the resulting tibial bone defects, in isolation and in combination with a screw osteosynthesis, and then biomechanically tested. Characteristics of the new mineral cements will then be optimized by modifying the polylactic-co-glycolic acid (PLGA) fibres, the length of the fibres and the 2-hydroxyethylmethacrylate (HEMA) concentration. The optimized mineral cements will then be biomechanically tested as bone substitutes for tibial head fractures in combination with different osteosyntheses and will be compared to a standard calcium phosphate cement. This will involve the specimens being systematically loaded using a cyclic loading protocol to simulate the lower loads associated with postoperative partial weight bearing and in a maximal loading protocol (Zwick Roell Z020, Ulm, Germany). The most promising bone substitute and osteosynthesis combinations will then be tested in human bones.The main hypothesis of this research is that the modified magnesium phosphate cements (dual-setting and fibre reinforced) in combination with osteosyntheses will display superior biomechanical properties compared to standard calcium phosphate cements.