Bridge Plate Design Effects on Yield and Fatigue in Distal Radius Fracture Model.

Abstract

Background Bridge plating for distal radius fractures is indicated for complex fractures with comminution, extensive articular involvement, and/or cases requiring immediate weight bearing. Bridge plate fixation of distal radius fractures is a well-documented treatment method; however, failures have been reported with repetitive loading through the bridged distal radius fracture. Plate design is implicated as a cause of plate fracture in select clinical studies but few mechanical tests comparing bridge plate designs have been reported. This study sought to determine the impact of plate design on bridge plates intended to allow for immediate weight-bearing. Methods Axial static ( n = 3) and dynamic testing ( n = 3) was performed on three distraction plates designs: bridge plate 1 (BP1) with central holes, bridge plate 2 (BP2) without central holes, and locking compression plate (BP3). Plates were loaded in axial compression with a simulated 10-mm fracture gap. Results Significant static load differences were noted between all groups. Static load to failure for BP1, BP3, and BP2 were 240 ± 5 N, 398 ± 9 N, and 420 ± 3 N, respectively ( p < 0.05). BP1 was the only plate series that failed during dynamic testing; all other plates achieved 100,000 cycles. Failure mode was a fracture occurring through the central screw hole of BP1. Finite element analysis demonstrated the effects of central screw holes on stress, strain, and plastic deformation under loading. Conclusion Unused screw holes are the mechanical weak points; plates designed without these central screw holes are expected to survive greater load values. The threshold for clinical importance will need to be determined by future studies.