多孔髓内针生物力学特性的有限元分析

Finite element analysis of biomechanical properties of the multihole intramedullary nail

背景:髓内针为长骨转移癌预防性内固定的常用选择之一,但存在锁钉周围应力集中,锁钉弯曲或折断等问题。选择更为坚强、持久的预防性内固定可有效改善骨转移癌患者的生存质量。目的:研究适用于长骨转移癌的多孔髓内针的生物力学特性,为选取打孔方案及生物力学试验提供理论依据。方法:采用有限元分析的方法,测量4种长骨髓内针打孔方案下截面刚度及整体刚度的变化,孔直径有2mm与3mm两种,导程有11mm与22mm两种。结果:孔直径2mm对截面拉压刚度及扭转刚度降低8.45%和8.13%,对平行于打孔平面方向的弯曲刚度几乎无影响,但在垂直于打孔平面方向的弯曲刚度降低15.96%。髓内针采取孔直径2mm、导程11mm、每导程4个孔、孔均匀布置的打孔方案,载荷下应力增长率及整体刚度改变最小。结论:髓内针侧壁打孔可造成髓内针刚度降低,孔周围出现应力集中的现象,影响髓内针的抗疲劳性。综合静态压缩、弯曲的分析结果,孔直径2mm,导程11mm,每导程4个孔,孔均匀布置的打孔方案的效果最佳。

Background：Intramedullary nail has been commonly used in preventive internal fixation for metastasis in long bones,but it is likely to be followed by problems like stress concentrating around the locking nail,bending or broken of the locking nail,etc.Selecting a stronger and more durable preventive internal fixation can effectively improve patients＇ quality of life.Objective：To investigate the biomechanical properties of the multihole intramedullary nail which is suitable for treating metastasis in long bones,and provide theoretical foundation for puncturing scheme selections and biomechanical experiments.Methods：Analyze the change of section rigidity and general rigidity of long-bone intramedullary nails under 4 different puncturing schemes by finite element analysis.The hole diameter is either 2mm or 3mm,and the lead is either 22 mm or 11 mm.Results：With 2 mm diameter holes,the pull-pressing rigidity and torsional rigidity were decreased by 8.45% and 8.13% on the section,and the bending rigidity was decreased by up to 15.96% on the direction vertical to the punctured section.But the diameter of the holes has no impact on the bending rigidity on the direction parallel to the punctured section.The intramedullary nail with a puncturing scheme of 2 mm diameter holes,11 mm leads,and 4 uniformly distributed holes per lead can load the lower stress growth rate and minimize the general rigidity.Conclusions：Puncturing on the side walls of the intramedullary nails can decrease the rigidity of intramedullary nails and cause stress concentrating around the nails.It will affect the fatigue resistance of the intramedullary nails.According to the comprehensive analysis results of the static compression and bending of the intramedullary nails,the puncturing scheme of 2 mm diameter holes,11 mm leads,and 4 uniformly distributed holes per lead can achieve the best curative effects.