Distal humerus internal fixation: a biomechanical comparison of 90° and parallel constructs

The optimal plating configuration for open reduction and internal fixation of complex distal humerus fractures is controversial. We evaluated cyclic fatigue performance and biomechanical stiffness in a cadaveric model of distal humerus fractures: precontoured nonlocking parallel plates versus a 90° nonlocking construct. A paired design was used, and 8 matched pairs of cadaveric arms were evaluated for bone density and plated. An osteotomy gap was created to simulate comminution, and constructs were randomized to anteroposterior, mediolateral, and torsional stiffness testing. Finally, 350 N was applied cyclically until deformation was permanent, Although there was a trend toward more stiffness of the parallel construct in anteroposterior, mediolateral, and torsional testing, it was not significant (P>.05). Likewise, there was no significant difference in number of cycles to failure (P>.05). Given these results, we suggest that it is reasonable to use a 90° construct or a parallel construct for internal fixation of distal humerus fractures. However, our findings are consistent with a trend in the biomechanical literature supporting use of a parallel construct.