股骨颈动力交叉钉联合空心钉治疗Pauwels Ⅱ型中青年股骨颈骨折的有限元分析

Finite element analysis of Pauwels Ⅱ type middle-aged and young femoral neck fracture fixed by dynamic cross screw system combined with cannulated screw

背景:股骨颈骨折是一种还未被解决的骨折,虽然涌现了空心螺钉、动力髋螺钉及股骨颈动力交叉钉等效果较好的植入物,但对于Pauwels角和剪切力较大的股骨颈骨折的最佳内固定方案尚无定论。目的:采用有限元分析法研究不同置钉位置的股骨颈动力交叉钉联合空心螺钉治疗PauwelsⅡ型中青年股骨颈骨折的生物力学特性。方法:根据提取的志愿者股骨CT数据建立Pauwels角为50°的股骨颈骨折模型,将股骨颈均分为3等分,构建4组模型:A组股骨颈动力交叉钉主钉位于股骨颈中间1/3;B组股骨颈动力交叉钉主钉位于股骨颈下1/3;C组股骨颈动力交叉钉主钉位于股骨颈下1/3+空心螺钉位于股骨颈上1/3;D组股骨颈动力交叉钉主钉位于股骨颈中间偏前内侧1/3+空心螺钉位于股骨颈中间偏后内侧1/3。在1200 N的载荷下测量4组股骨、内固定模型的应力分布及峰值、最大变形情况和骨折断面的应力分布。结果与结论:①通过有限元分析可知,C组的股骨及内固定模型的应力分布及峰值、最大变形情况和骨折断面的应力均小于其余3组;②B组相较于A组有着更小的股骨骨质、内固定物和骨折断面应力和位移,说明股骨颈动力交叉钉头钉放置于股骨颈下1/3比中1/3更稳定;③结果表明,股骨颈动力交叉钉头钉位于股骨颈下1/3联合股骨颈上1/3平行放置螺钉对青壮年PauwelsⅡ型股骨颈骨折具有更好的稳定性,是治疗该类型骨折的有效选择。

BACKGROUND:Femoral neck fracture is a kind of unsolved fracture.Although cannulated screw,dynamic hip screw,and femoral neck dynamic cross screw have emerged,the best internal fixation scheme for femoral neck fracture with large Pauwels angle and shear force has not been unified.OBJECTIVE:To investigate biomechanical properties of femoral neck dynamic cross screw combined with cannulated screw in the treatment of Pauwels II type middle-aged and young femoral neck fractures using finite element analysis.METHODS:According to the extracted CT data of volunteers’femur,the model of femoral neck fracture with Pauwels angle of 50°was established,and the femoral neck was divided into three equal parts.Four groups of models were constructed:In group A,main nail of femoral neck dynamic cross screw was located in the middle 1/3.In group B,main nail of femoral neck dynamic cross screw was located in the lower 1/3.In group C,main nail of femoral neck dynamic cross screw was located at the lower 1/3+cannulated screw at the upper 1/3.In group D,main nail of femoral neck dynamic cross screw was located in the anterior medial part of the middle 1/3+cannulated screw was located in the medial posterior medial part of the middle 1/3.The stress distribution,peak value,maximum deformation,and stress distribution of fracture section of four groups of femur and internal fixation models were measured under 1200 N load.RESULTS AND CONCLUSION:(1)The finite element analysis showed that the stress distribution and peak value,the maximum deformation and the stress of the fracture section of the femur and internal fixation model in group C were less than those in the other three groups.(2)Compared with group A,group B had smaller stress and displacement of femoral bone,internal fixation,and fracture section,indicating that the placement of head nail of femoral neck dynamic cross screw at the lower 1/3 of the femoral neck was more stable than that of middle 1/3.(3)The results show that the head nail of femoral neck dynamic cross screw located at the lower 1/3 of the femoral neck and 1/3 parallel screws on the femoral neck is more stable for Pauwels II femoral neck fracture in young adults,and it is a good choice for the treatment of this type of fracture.