Liu Fei, Feng Xiaoreng, Zheng Jianxiong, Leung Frankie, Chen Bin
Division of Orthopaedics and Traumatology, Department of Orthopaedics, Nanfang Hospital, Southern Medical University, Guangzhou, China.
Department of Orthopaedics and Traumatology, Yangjiang People's Hospital, Yangjiang, China.
Front Bioeng Biotechnol. 2022 Oct 28;10:1019172. doi: 10.3389/fbioe.2022.1019172. eCollection 2022.
To compare the fixation stability of the lag screw with a undercut thread design for the dynamic hip screw (DHS) system the lag screw with the conventional buttress thread. The lag screws with the undercut thread (a flat crest feature, a tip-facing undercut feature) and buttress thread were both manufactured. Fixation stability was investigated using cyclic compressive biomechanical testing on custom osteoporotic femoral head sawbone. The forces required for the same vertical displacement in the two types of lag screw were collected to evaluate the resistance to migration. Varus angle was measured on X-ray images to assess the ability in preventing varus collapse. Finite element analysis (FEA) was performed to analyze the stress and strain distribution at the bone-screw interface of the two types of lag screws. The biomechanical test demonstrated that the force required to achieve the same vertical displacement of the lag screw with the undercut thread was significantly larger than the lag screw with conventional buttress thread ( < 0.05). The average varus angles generated by the undercut and buttress threads were 3.38 ± 0.51° and 5.76 ± 0.38°, respectively ( < 0.05). The FEA revealed that the region of high-stress concentration in the bone surrounding the undercut thread was smaller than that surrounding the buttress thread. The proposed DHS system lag screw with the undercut thread had higher migration resistance and superior fixation stability than the lag screw with the conventional buttress thread.
为比较动力髋螺钉（DHS）系统中带有倒牙设计的拉力螺钉与传统支撑螺纹拉力螺钉的固定稳定性。制造了带有倒牙（平牙顶特征、尖端朝向的倒牙特征）和支撑螺纹的拉力螺钉。在定制的骨质疏松性股骨头锯骨模型上进行循环压缩生物力学测试，以研究固定稳定性。收集两种类型拉力螺钉在相同垂直位移下所需的力，以评估抗移位能力。在X射线图像上测量内翻角度，以评估防止内翻塌陷的能力。进行有限元分析（FEA），以分析两种类型拉力螺钉在骨-螺钉界面处的应力和应变分布。生物力学测试表明，带有倒牙的拉力螺钉在达到相同垂直位移时所需的力明显大于带有传统支撑螺纹的拉力螺钉（P<0.05）。倒牙和支撑螺纹产生的平均内翻角度分别为3.38±0.51°和5.76±0.38°（P<0.05）。有限元分析显示，倒牙周围骨中的高应力集中区域小于支撑螺纹周围的区域。所提出的带有倒牙的DHS系统拉力螺钉比带有传统支撑螺纹的拉力螺钉具有更高的抗移位能力和更好的固定稳定性。
