Biomechanical Study of Load to Failure of a Bone Model After Removal of a 2.7-mm or 3.5-mm Plate

Objective This study aimed to investigate the impact of screw hole size on the mechanical strength of bone models following construct removal. Methods A locking plate and screws were applied to 34 cylindrical bone models. Seventeen (50%) models were assigned to receive a six-hole plate with 6 3.5-mm screws, and seventeen (50%) models were assigned to receive a ten-hole plate with 8 2.7-mm screws. The screws were subsequently removed, and each model underwent three-point bending and compression tests until bone model failure. Non-inferiority analysis was performed comparing the maximum failure load of the 3.5-mm construct to the 2.7-mm construct. A non-inferiority limit was set at a 10% reduction in the 2.7-mm bone model mean maximum failure load for both the compression and three-point bending tests. Results For three-point bend testing, the six-hole 3.5-mm construct was found to be non-inferior to the eight-hole 2.7-mm construct (2145.56 ± 141.04 N versus 2228.37 ± 174.93 N). For compression testing, the 3.5-mm construct cohort was non-inferior to the 2.7-mm construct cohort (14097.73 ± 686.88 N versus 14782.31 ± 841.95 N). Conclusion Our bone model data suggest that the biomechanical strength of bone following 3.5-mm construct removal is non-inferior to the biomechanical strength of bone following 2.7-mm construct removal. When selecting fixation that may be later removed, surgeons should choose plate constructs for open reduction and internal fixation that are suited to the fracture fixation without concern that screw hole size affects the biomechanical strength of the bone after hardware removal.