Biomechanics of four techniques for fixation of the four-part humeral head fracture

Abstract

Objective: To carry out a biomechanical study among four techniques for fixation of four-part humeral head fractures. Methods: The fracture was reproduced in 40 plastic humeri, divided into four groups of ten models, according to the fixation technique, each one employing different fixation resources, in different configurations. The humeral models were mounted on an aluminum scapula, with leather straps simulating the rotator cuff tendons, and submitted to bending and torsion tests in a universal testing machine, using relative stiffness asan evaluation parameter. Assemblies with intact humeri were analyzedfor comparison. Results: The biomechanical behavior of the fixation techniques varied within a wide range, where the assemblies includingthe DCP plate and the 4.5mm diameter screws were significantly more rigid than the assemblies with the Kirschner wires and the 3.5mm diameter screws. Conclusion: The four fixation techniques were able to bear loads compatible with physiological demands, but those with higherrelative stiffness should be preferred for clinical application. Laboratory investigation.