Fixation of extra-articular distal humerus fractures using one locking plate versus two reconstruction plates: a laboratory study.

OBJECTIVE: To compare the strength and stiffness of standard double-plate fixation with that of a single-locking plate for comminuted extra-articular distal humeral fractures.

MATERIALS: Eight matched pairs of humeri were used. One of each pair was fixed with two 3.5-mm standard reconstruction plates applied dorsally; the other was fixed with one precontoured locking plate applied to the posterior aspect of the lateral column. A 1-cm gap was created to simulate a distal fracture model with 100% metaphyseal comminution with no bony apposition. Stiffness testing of these constructs was performed in axial compression, anterior, posterior and lateral bending, and torsion. They were then cyclically loaded for 4000 cycles with 60 N in posterior bending and the stiffnesses retested. Finally, each construct was posteriorly loaded to failure to determine its ultimate strength.

RESULTS: The double-plate construct was significantly stiffer than the one locking plate construct in anterior bending (39%; p = 0.02), posterior bending (23%; p = 0.04), and lateral bending (60%; p = 0.01). No significant stiffness differences were seen in axial compression and torsion (p = 0.64 and 0.25, respectively). After cyclic loading, all construct stiffnesses were relatively unchanged. Both construct types had similar failure strengths (p = 0.76) of approximately 400 N.

CONCLUSIONS: Double-plating provides a more rigid fixation than a single-locked plate for fixation of extra-articular comminuted distal humeral fractures. This could be clinically relevant in situations with 100% comminution as seen in gun shot injuries.