Biomechanical comparison of three fixation methods under axial loading in proximal humerus fractures with medial...

This study aims to compare the biomechanical performance of three different surgical fixation techniques in the treatment of proximal humerus fractures with medial metaphyseal defects.

A total of 24 synthetic humerus bone models were used and equally divided into three groups (n = 8 per group). A standardized unstable proximal humerus fracture model with a medial metaphyseal cortical defect extending to the surgical neck was created using a three-dimensional (3D)-printed osteotomy guide. Group 1 received fixation with a lateral anatomical locking plate. Group 2 was treated with a combination of a lateral anatomical plate and a medial buttress plate (dual plating). Group 3 underwent fixation with an intramedullary nail (IMN); in this group, four specimens had distal locking with an endopin (Group 3a), and the other four with static screws (Group 3b). All specimens were subjected to axial loading until failure. Forces at the onset of failure and complete failure were recorded, and fracture patterns were documented.

In Groups 1 and 2, transverse fractures consistently occurred at the level of the most distal screw of the lateral plate. In Group 3, failure was observed either proximally or distally at the nail tip, including butterfly fragment formation and metaphyseal collapse. Group 2 exhibited the highest resistance to axial loading, followed by Group 1 and Group 3, with statistically significant differences between all groups (p = 0.043, p = 0.0003, p < 0.00001). No significant difference was found between subgroups 3a and 3b (p > 0.05).

Our study results indicate that double plating provides the greatest axial stability in proximal humerus fractures with medial metaphyseal defects, supporting its use in fracture patterns with medial column deficiency. However, as fixation choice should be guided by patient-specific factors and surgical feasibility, these findings should be interpreted in the context of experimental conditions and loading limitations.