A Preliminary Mechanical Evaluation of a Newly Developed Polyaxial Locking Mechanism for a Distal Radius Plate

Background/Objectives: Polyaxial locking systems for distal radius plates differ among manufacturers, and the mechanical strength of their locking mechanism is rarely disclosed. This study aimed to perform a preliminary mechanical evaluation of a newly developed polyaxial locking mechanism and to investigate its strength at different screw insertion angles. Methods: The polyaxial locking mechanism was evaluated via static load testing at three screw insertion angles until failure, and the maximum bending moment was measured. Loading was performed via cantilever bending to generate a bending moment in the polyaxial locking mechanism. The maximum bending moments of the insertion angles of 10° for the holes in the distal rows were investigated for significant differences. Results: Maximum bending moments significantly decreased as the screw insertion angle increased, with reductions of approximately 50% at 5° and 10° compared with 0°. At a 10° insertion angle, variation in ultimate strength was observed among screw hole in the distal row. The failure mechanism was loosening of the locking screws in all tests. Conclusions: The maximum bending moment of the polyaxial locking mechanism decreased with increasing locking screw insertion angle, highlighting the importance of insertion angle in polyaxial locking plate fixation.