Application of a lateral intertubercular sulcus plate in the treatment of proximal humeral fractures: a finite element analysis

Background Inversion deformities caused by insufficient medial support are especially common when the PHILOS locking plate is used to treat proximal humeral fractures. Using finite element analysis, we aimed to compare the biomechanical properties of a PHILOS locking plate (PLP) and a PLP combined with a lateral intertubercular sulcus plate (PLP-LSP) in the fixation of proximal humeral fractures with loss of the medial column. Methods After creating a three-dimensional finite element model of a proximal humeral fracture with loss of the medial column, three implant models were established. A full-screw PLP was used in Group A, a PHILOS plate lacking medial screw support and an additional steel plate (MPLP-LSP) were used in Group B, and a full-screw PLP-LSP was used in Group C. The three fixation models were applied to the proximal humeral fracture model, following which horizontal, compressive, and rotational loads were applied to the humerus model. We evaluated structural stiffness and stress distribution in the implant and compared displacement and angle changes among the three models. Results Displacement and angle changes were smallest in Group C (PLP-LSP). The implant model used in Group C also exhibited greater structural rigidity, endured less von Mises stress, and was more stable than the models used in Group A and Group B. Conclusion An LSP placed at the intertubercular sulcus provides effective lateral and medial support, thereby reducing stress on the PLP and providing better stability with proximal humeral fractures.