Enhanced construct stability with a locking plate system integrated into 3D-printed titanium implants for bone defect...

Fixation stability is critical for successful osseointegration of 3D-printed implants in segmental bone defect reconstruction. Although locking plate systems offer theoretical advantages over nonlocking systems, particularly in osteoporotic or high-load-bearing bones, their application in 3D-printed implants remains limited owing to manufacturing challenges. We aimed to evaluate the mechanical performance of locking versus nonlocking fixation in 3D-printed titanium implants. We hypothesized that locking fixation provides superior construct stability and fatigue resistance.

Standardized synthetic bone cylinders were assembled using custom-designed 3D-printed titanium implants featuring integrated plate systems compatible with locking and nonlocking screws. Constructs were divided into two groups based on fixation method: nonlocking (n = 11) and locking (n = 11). Mechanical performance was assessed through static three-point bending (n = 6 per group) and cyclic torsional fatigue (n = 5 per group) tests. Key outcome measures included yield load, failure mode, torsional stiffness over time, and survival rate under fatigue loading.

Locked constructs exhibited a significantly higher yield load under bending than nonlocked constructs (p = 0.003), indicating better resistance to irreversible deformation. Failure analysis revealed stress concentration at the innermost screw hole in the nonlocked constructs. In contrast, stress was more evenly distributed in the locked constructs, leading to bone cylinder fractures at the screw farthest from the defect. Under cyclic torsional loading, all the locked constructs survived the testing protocol, maintaining a better initial stiffness, whereas the nonlocked constructs showed progressive stiffness degradation with a 60% failure rate.

Locking fixation improves construct stability and fatigue resistance in 3D-printed titanium implants for bone defect reconstruction, supporting its integration into additive-manufactured implants. Future in vivo animal studies, incorporating patient-specific designs and complex loading conditions are required to validate the clinical utility of this approach.