Biomechanical comparison of crossed Kirschner wires fixation for supracondylar humerus fractures at different fracture lines: finite element analysis and exploration of the optimal fixed angle

Supracondylar humerus fractures(SHFs) are common in children, but the biomechanical stability of Kirschner wire (K-wire) fixation at different fracture levels has not been adequately investigated. This study aimed to compare the biomechanical characteristics of crossed K-wire fixation for SHFs with different fracture levels using finite element analysis (FEA) and to identify the optimal pin configuration, thereby providing a biomechanical basis for personalized surgical planning. A total of 27 types of finite element models were constructed, which showed different insertion angles of crossed K-wires based on the low fracture, the middle fracture, and the high fracture of SHFs. The equivalent (von Mises) stress, equivalent elastic strain, and total deformation were analyzed. The FEA results demonstrated distinct biomechanical characteristics across different fracture levels. For low fractures, smaller insertion angles for the crossed K-wires provided more favorable biomechanical performance. For middle fractures, a configuration combining a larger lateral insertion angle with a smaller medial insertion angle appeared to offer superior mechanical stability. For high fractures, crossed fixation using large insertion angles on both sides showed more favorable biomechanical characteristics. The study established a biomechanical relationship between fracture level and the optimal configuration of crossed K-wire fixation in SHFs. The findings can serve as a reference for optimizing the fixation techniques of the SHFs.