Introduction: Concerning rates of nonunion in articular distal humerus fractures indicate an unsolved problem. The fixation principles of O'Driscoll describe linking the fractured articular segment to the distal humerus columns with compression screws which creates a stable fixed angle construct. A novel device has been introduced which utilizes an interlocking beam through the articular segment to connect the distal aspect of the medial and lateral plates, creating a linked construct. We sought to evaluate the stability of this linked construct using an articular model of distal humerus fracture.
Materials and methods: Ten matched pair specimens of 65 years of age or older were randomized to the use (LB group) or non-use (NLB group) of an interlocking beam to link the medial and lateral locking plates in fixation of an AO Type C3 fracture model. Outside of the linking beam, fixation between the matched pairs was consistent using 2.7 mm locking screws distally with fixed trajectories and +/- 2 mm lengths.
Results: Mean stiffness was 273 Newtons/mm in the LB group and 225 Newtons/mm in the NLB group (p = 0.001). Mean maximum displacement was 0.28 in the LB group and 0.93 mm in the NLB group (p = 0.006). Mean load to failure was 277 pounds in the LB group and 280 pounds in the NLB group (p = 0.94).
Discussion: Our results indicate that an interlocking beam which links the medial and lateral plates provides greater stability compared to a similar construct without an interlocking beam. We attribute this finding to the beam's double supported design which resists cantilever bending and provides robust compression of the fractured fragments.
Keywords: Distal humerus columns; Distal humerus fracture; Intra-articular fracture; Locked plating; Parallel plating; Screw interdigitation.
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