The Role of Proximal Locking Fixation in Volar Distal Radius Fracture Fixation.

Background  Volar-locked plating has become a popular treatment option for unstable distal radius fractures. While using locking screws in the distal fragment increases the stability of the fixation, the biomechanical benefits of locking fixation in the proximal fragment have not been definitively established. Purposes  This study evaluated the initial mechanical behavior of the volar plating construct with different locking screw configurations in the proximal fragment. Materials and Methods  Sixteen Sawbones radius models were used. An unstable metaphyseal distal radius fracture was created and fixated with a volar-locked plate. Four different screw configurations in the proximal fragment were tested: all nonlocking screws, locking screw in the distal-most hole, locking screw in the proximal-most hole, and locking screws in both the proximal- and distal-most holes. Initial stiffness, displacement during harmonic loading, and load-to-failure were compared among the three groups. Results  The initial stiffness, displacement during harmonic loading, and load-to-failure did not significantly differ among the four proximal screw configurations ( p  < 0.05). Failure occurred via toggling of the screws in the configuration with all nonlocking screws and through screw breakage or locking mechanism failure in the configurations with locking screws. Conclusion  The use of locking screws in the proximal fragment did not significantly affect the initial stability of volar distal radius plating. However, failure modes differed between the nonlocking and locking configurations, consistent with known mechanical properties of locking fixation. Further mechanical studies in cadaveric models and clinical trials are warranted to determine the optimal screw configuration in volar distal radius plating. Level of Evidence  To be determined. Biomechanical study on synthetic models.