BACKGROUND:Intramedullary nails and locking plates are widely used in the treatment of proximal humeral fractures,but there is no consensus on the choice of internal fixation. OBJECTIVE:To compare the biomechanical stability of intramedullary nails and locking plates in the treatment of two-part and three-part proximal humeral fractures by finite element analysis. METHODS:CT data of the humerus of a volunteer were collected and imported into Minics 21.0,Geomagic Wrap,Soildwork 2017,and Abaqus 2021 to establish finite element models of two-part and three-part fractures treated with two internal fixation methods,respectively.Group A:two-part fracture fixed with intramedullary nail model;group B:two-part fracture fixed with locking plate model;group C:three-part fracture fixed with intramedullary nail model;group D:three-part fracture fixed with locking plate model.The stress distribution,displacement degree,and maximum value of the humerus and internal fixation were compared and analyzed. RESULTS AND CONCLUSION:(1)The maximum stress and maximum displacement of the humerus were the smallest in the model of group A,and the maximum stress and maximum displacement of the humerus were the largest in the model of group D.The stress of the locking plate group was mainly concentrated in the medial inferior part of the humeral head and the screw hole area,while the stress of the intramedullary nail group was mainly concentrated around the fracture line and the lateral inferior part of the surgical neck of the humerus.There is no significant difference in displacement distribution between the two.It is mainly concentrated in the distal humerus.(2)The maximum stress value of the intramedullary nail was the lowest in the model of group A,and the maximum stress value of the locking plate was the highest in the model of group D.The maximum stress of the two internal fixations was mainly concentrated in the talar screw and the connection with the internal fixation.The stress cloud distribution of the locking steel plate was concentrated,while the stress cloud distribution of the intramedullary nail was more uniform.(3)The results showed that compared with the locking plate,the intramedullary nail had more biomechanical advantages,and this advantage was more obvious in three-part fractures.