BACKGROUND:Unstable femoral neck fracture with anterior medial bone defect is very rare and difficult to manage.The best internal fixation scheme for the treatment of this kind of fracture has been a controversial topic among orthopedic surgeons.OBJECTIVE:To evaluate the biomechanical properties of different internal fixation in the treatment of Pauwels Ⅲ femoral neck fracture with anterior medial defect by finite element analysis in order to provide experimental support for clinical operation decision.METHODS:The models of femoral neck fracture with anterior medial defect and Pauwels angle of 70° were constructed by Mimics 21.0,Geomagic,and Solidworks software.Three internal fixation methods were simulated:group A(3 hollow nails+medial plate),group B(femoral neck dynamic crossover nail+1 hollow nail),and group C(4 hollow nails"diamond fixation").The stress and displacement changes of femur,internal fixation,and femoral head were analyzed under 2 100 N load of 3 times body weight.RESULTS AND CONCLUSION:(1)The overall stress of the femur in group A was the smallest,and the force was more uniform and dispersed.The stress of the internal fixation model in group B was smaller,indicating that it had a better effect of stress dispersion and shear resistance.The stress on the stress side of the femur in group A was significantly lower than that in the other two groups,and there was no stress concentration.(2)The displacement of the whole femoral model,internal fixation or femoral head in group A was less than that in the other two groups,indicating that"hollow nail combined with medial plate"could play a better stabilizing role and could better reduce the occurrence of hip varus.(3)The application of three screws combined with medial supporting plate in vertical,unstable and anteromedial bone defect of femoral neck fracture can significantly improve the stability of fracture and resistance to deformation.It is a good choice for the treatment of this type of fracture.

BACKGROUND:Unstable femoral neck fracture with anterior medial bone defect is very rare and difficult to manage.The best internal fixation scheme for the treatment of this kind of fracture has been a controversial topic among orthopedic surgeons.OBJECTIVE:To evaluate the biomechanical properties of different internal fixation in the treatment of Pauwels Ⅲ femoral neck fracture with anterior medial defect by finite element analysis in order to provide experimental support for clinical operation decision.METHODS:The models of femoral neck fracture with anterior medial defect and Pauwels angle of 70° were constructed by Mimics 21.0,Geomagic,and Solidworks software.Three internal fixation methods were simulated:group A(3 hollow nails+medial plate),group B(femoral neck dynamic crossover nail+1 hollow nail),and group C(4 hollow nails"diamond fixation").The stress and displacement changes of femur,internal fixation,and femoral head were analyzed under 2 100 N load of 3 times body weight.RESULTS AND CONCLUSION:(1)The overall stress of the femur in group A was the smallest,and the force was more uniform and dispersed.The stress of the internal fixation model in group B was smaller,indicating that it had a better effect of stress dispersion and shear resistance.The stress on the stress side of the femur in group A was significantly lower than that in the other two groups,and there was no stress concentration.(2)The displacement of the whole femoral model,internal fixation or femoral head in group A was less than that in the other two groups,indicating that"hollow nail combined with medial plate"could play a better stabilizing role and could better reduce the occurrence of hip varus.(3)The application of three screws combined with medial supporting plate in vertical,unstable and anteromedial bone defect of femoral neck fracture can significantly improve the stability of fracture and resistance to deformation.It is a good choice for the treatment of this type of fracture.