Okazaki Yoshimitsu, Hayakawa Emiko, Tanahashi Kazumasa, Mori Jun
Department of Life Science and Biotechnology, National Institute of Advanced Industrial Science and Technology, 1-1 Higashi 1-chome, Tsukuba, Ibaraki 305-8566, Japan.
TANAC Co., Ltd., 4-24 Moto-Machi, Gifu-city, Gifu 500-8185, Japan.
Materials (Basel). 2020 Oct 29;13(21):4836. doi: 10.3390/ma13214836.
To evaluate mechanical performance properties of various types of cortical bone screw, cancellous bone screw, and locking bolt, we conducted torsional breaking and durability tests, screw driving torque tests into bone models, and screw pullout tests (crosshead speed: 10 mm/min) after driving torque tests. The 2° proof and rupture torques of a screw, which were estimated from torque versus rotational angle curves, increased with increasing core diameter of the screw. The durability limit of metallic screws obtained by four-point bending durability tests increased with increasing core diameter. The compressive, tensile, and shear strengths of the bone models used for the mechanical testing of orthopedic devices increased with increasing density of the bone model. The strength and modulus obtained for solid rigid polyurethane foam (SRPF) and cellular rigid polyurethane foam (CRPF) lay on the same straight line. Among the three strengths, the rate of increase in compressive strength with the increase in density was the highest. The maximum torque obtained by screw driving torque tests for up to 8.3 rotations (3000°) into the bone models tended to increase with increasing core diameter. In particular, the maximum torque increased linearly with increasing effective surface area of the screw, as newly defined in this work. The maximum pullout load increased linearly with increasing number of rotations and mechanical strength of the bone model. Screws with low driving torque and high pullout load were considered to have excellent fixation and are a target for development.
为评估各类皮质骨螺钉、松质骨螺钉和锁定螺栓的机械性能，我们进行了扭转断裂和耐久性测试、将螺钉拧入骨模型的拧入扭矩测试以及在拧入扭矩测试后进行的螺钉拔出测试（十字头速度：10毫米/分钟）。根据扭矩与旋转角度曲线估算出的螺钉2°屈服扭矩和断裂扭矩随螺钉芯直径的增加而增大。通过四点弯曲耐久性测试得到的金属螺钉的耐久性极限随芯直径的增加而提高。用于骨科器械力学测试的骨模型的抗压、抗拉和抗剪强度随骨模型密度的增加而提高。实心刚性聚氨酯泡沫（SRPF）和多孔刚性聚氨酯泡沫（CRPF）的强度和模量位于同一直线上。在这三种强度中，抗压强度随密度增加的增长率最高。在骨模型中进行多达8.3次旋转（3000°）的螺钉拧入扭矩测试所获得的最大扭矩倾向于随芯直径的增加而增大。特别是，如本研究新定义的那样，最大扭矩随螺钉有效表面积的增加呈线性增大。最大拔出载荷随旋转次数和骨模型机械强度的增加呈线性增大。驱动扭矩低且拔出载荷高的螺钉被认为具有优异的固定性能，是开发的目标。
