A biomechanical analysis of four humeral fracture fixation systems

A biomechanical study was initiated to compare four fracture fixation devices: the AO dynamic compression plate, a distal fin locking nail, a solid locked intramedullary nail, and paired flexible nails for humeral fracture fixation. Eighteen pairs of fresh-frozen, intact humeri were harvested, standardized midshaft transverse osteotomies were created in each specimen, and left and right specimens were fixed with plates and nails, respectively. The bending properties of the plate-fixed humeri were significantly greater than the nailed humeri in both the anteroposterior and mediolateral planes on a paired basis. The distal fin nail and solid locked nail had comparable bending properties, and both had bending properties superior to those measured for the paired flexible nails. The torsional properties of humeri fixed with plates and solid locked nails were equivalent, except for rigidity and stiffness, which were superior for the nail. Both fixation methods resulted in torsional properties significantly greater to those measured for humeri fixed with paired flexible nails or a distal fin nail.