Comparison of distal humerus fracture fixation: a biomechanical study.

Few biomechanical studies have been done evaluating the rigidity of internal fixation constructs for distal humerus fractures. We assessed the bending and torsional stiffness of five commonly used multiple plate constructs. Plates were applied in three positions: medially, along the medial supracondylar column; laterally, along the lateral supracondylar column; or posterolaterally, extending distally to the capitellum. Each specimen was randomly assigned to one of five construct groups. All plated specimens were stiffer in the frontal plane as compared with the sagittal plane and, when compared with intact specimens, showed a disproportionate decrease in sagittal plane stiffness. Constructs 1 and 5 had significantly greater relative bending stiffness in the sagittal plane than constructs 3 and 4. Construct 4 had the lowest relative bending stiffness in the frontal plane. This reached statistical significance when compared with constructs 2 and 5. There was no significant difference in the torsional stiffness of the five constructs. We conclude that the multiple plate constructs offered significantly less bending stiffness than the intact specimens, with a particular deficiency in the sagittal plane. The triple-plated construct (construct 5) did not confer greater stiffness and was technically difficult to implant. The medial pelvic reconstruction plate combined with the posterolateral DCP (construct 1) provided the greatest sagittal plane stiffness, in addition to comparable frontal plane and torsional stiffness. We recommend its use in the treatment of fractures of the distal humerus.