The use of a screw for repairing defected bones is limited by the dilemma between stiffness, bioactivity and internal fixation ability in current products. For polymer bone screw, it is difficult to achieve the bone stiffness and osteo-induction. Polymer composites may enhance bioactivity and mechanical properties but sacrifice the shape memory properties enormously. Herein, we fabricated a programmable bone screw which is composed of shape memory polyurethane, hydroxyapatite and arginylglycylaspartic acid to resolve the above problem. This composite has significantly improved mechanical and shape-memory properties with a modulus of 250 MPa, a shape fixity ratio of ~90% and a shape recovery ratio of ~96%. Moreover, shape fixity and recovery ratios of the produced SMPC screw in the simulative biological condition were respectively ~80% and ~82%. The produced screw could quickly recover to its original shape in vitro within 20 s leading to easy internal fixation. Additionally, the composite could support mesenchymal stem cell survival, proliferation and osteogenic differentiation in vitro tests. It also promoted tissue growth and showed beneficial mechanical compatibility after implantation into a rabbit femoral intracondyle for 12 weeks with little inflammation. Such bone screw exhibited a fast-fixing, tightened fitting, enhanced supporting and boosted bioactivity simultaneously in the defective bone, which provides a solution to the long-standing problem for bone repairing. We envision that our composite material will provide valuable insights into the development of a new generation of bone screws with good fixation and osteogenic properties. STATEMENT OF SIGNIFICANCE: The main obstacles to a wider use of a bone screw are unsatisfied stiffness, inflammatory response and screw loosening issues. Herein, we report a programmable screw with mechanically robust, bioactive and fast-fixing performances. The shape memory polymer composite takes advantage of the component in the natural bone and possesses a stable bush-like structure inside through the covalent bonding, and thus achieve significantly improved mechanical and memory properties. Based on its shape memory effect, the produced screw was proved to offer a recovery force to surroundings and promote the bone regeneration effectively. Therefore, the composite realizes our expectations on functions through structure design and paves a practical and effective way for the development of a new generation of bone screws.

中文翻译：

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可编程，快速固定，骨再生，生物力学坚固的骨螺钉。

在目前产品中，刚度，生物活性和内部固定能力之间的两难选择限制了使用螺钉修复缺损的骨头。对于聚合物接骨螺钉，很难实现骨刚度和骨诱导。聚合物复合材料可以增强生物活性和机械性能，但极大地牺牲了形状记忆性能。在此，我们制造了由形状记忆聚氨酯，羟基磷灰石和精氨酰基糖基葡萄糖酸天冬氨酸组成的可编程接骨螺钉，以解决上述问题。该复合材料的模量为250 MPa，形状固定率约为90％，形状恢复率约为96％，具有显着改善的机械和形状记忆性能。而且，在模拟生物学条件下，所生产的SMPC螺钉的形状固定性和恢复率分别为〜80％和〜82％。所产生的螺钉可以在20秒内在体外迅速恢复到其原始形状，从而易于进行内部固定。此外，该复合材料可以支持间充质干细胞的存活，增殖和体外成骨分化。植入兔股骨intra内12周后几乎没有发炎，它还促进了组织生长并显示出有益的机械相容性。这样的骨螺钉在缺损的骨头中同时表现出快速固定，拧紧的装配，增强的支撑和增强的生物活性，这为长期存在的骨头修复问题提供了解决方案。我们设想，我们的复合材料将为开发具有良好固定和成骨特性的新一代骨螺钉提供有价值的见识。重要性声明：广泛使用接骨螺钉的主要障碍是不满意的刚度，炎症反应和螺钉松动问题。本文中，我们报告了一种具有机械强度，生物活性和快速固定性能的可编程螺钉。形状记忆聚合物复合材料利用了天然骨中的成分，并通过共价键合在内部具有稳定的灌木状结构，从而显着提高了机械和记忆性能。基于其形状记忆效果，证明了所生产的螺钉能够向周围环境提供恢复力并有效地促进骨骼再生。因此，复合材料通过结构设计实现了我们对功能的期望，并为开发新一代接骨螺钉铺平了实用而有效的途径。