Feasibility of Integrating Locking Plate System into Additively Manufactured Implants: A Mechanical Comparison of Three-Dimensional-Printed and Machined Locking Hole Threads.

Abstract

This study integrated a locking plate system into three-dimensional (3D)-printed implants and evaluated whether directly 3D-printed locking plate holes could achieve mechanical performance comparable to their machined counterpart. In vitro mechanical tests were performed to compare a 3D-printed 3.5-mm locking plate system with a commercially available variable-angle locking system (ARIX). Locking plate specimens (n = 90) were 3D printed from Ti6Al4V in three build orientations (0, 45 and 90 degrees). A torque limit test assessed the failure points under three screw insertion torques (0.6, 1.1 and 2.0 Nm) at two angles (0 and 15 degrees). The locked screw-and-plate constructs then underwent push-out testing, with a load applied parallel to the screw axis.At 2.0 Nm, all 3D-printed specimens failed due to thread deformation, whereas the ARIX system remained intact. Specimens printed at 0-degree orientation had the highest push-out strength, comparable to ARIX plates, while those printed at 90 degrees showed significantly lower strength. A higher insertion torque (1.1 Nm) improved the push-out strength regardless of screw angulation. Low torque with angled screws led to a substantial reduction in push-out strength.The directly 3D-printed locking plate system achieved a comparable mechanical performance to machined counterparts when printed at 0-degree orientation, with appropriate torque. Optimal build orientation and careful control of insertion torque are crucial for maximizing the performance of 3D-printed locking plates.