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 1 200 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.

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 1 200 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.