Biomechanical Comparison of Dorsal Wrist Spanning Plates Versus External Fixation in Distal Radius Fractures With a Simultaneous Axial and Bending Load.

Abstract

Introduction: External fixators have traditionally been used for comminuted distal radius fractures not amenable to plate fixation but are associated with complications. Dorsal spanning plates have emerged as an alternative. Prior biomechanical studies comparing these constructs typically assess forces in a single vector. This study compares dorsal spanning plates and external fixators under combined axial loading with simultaneous flexion, extension, radial, and ulnar bending to better replicate physiologic wrist forces.

Methods: Twenty-four identical laser-sintered bone models were created, with 12 assigned to the dorsal spanning plate group and 12 to the external fixator group. Constructs were tested using a servohydraulic test machine under combined axial and bending loads. Stiffness, maximum load, and yield load were recorded. Statistical analysis was performed using the Mann-Whitney U test with Monte Carlo exact testing.

Results: The dorsal spanning plate group demonstrated significantly greater stiffness than the external fixator group in radial and ulnar deviation. No significant differences in stiffness, maximum load, or yield load were observed between groups during flexion. In extension, the plate group exhibited significantly higher maximum load, while stiffness and yield load were not statistically different.

Conclusion: Dorsal spanning plates demonstrate increased stiffness compared with external fixators under physiologic multivector loading. These findings may support their use in patients expected to load the wrist postoperatively, such as individuals with polytrauma or elderly patients reliant on assistive walking devices.