Mechanical Behaviour of a Fracture Fixation Orthopaedic Implant for Proximal Tibia Bone, a Validated Finite Element Analysis

Fracture fixation orthopaedic implants are essential for functional and structural recovery of injured bones. As their physical, mechanical, and topological properties contribute to their success rate, understanding implants behaviour under load bearing experiments is crucial. The aim of this study is to develop a Finite Element (FE) model for a newly designed proximal tibia orthopaedic implant and to analyse its mechanical behaviour under compressive loading. To prepare a bone sample with the mechanical properties of an aged human tibia, a male bovine tibia bone was demineralized in 1.2M hydrochloric acid (HCL) for 30hrs. After conducting the experiments on the bone sample, it was 3D scanned and exported to the FE software for computational analysis. To cover the usual daily load bearing activities including single limb stance, gait, and slow-paced run (swing phase) for a 120kg patient, 6kN load was applied on the model of the intact bone and the computational results were validated with the derived experimental data. Afterward, FE analysis was continued with up to 30kN load, and the mechanical properties such as equivalent plastic strain, ductile damage criterion and damage evolution were evaluated for the implant and its locking screws. Although no full element failure was detected, some nodes failed on the screw surface nearest to the implant neck making it most vulnerable to fail under higher loads or as a result of cyclic loading and fatigue failure. The results pointed out that the newly designed implant would sustain under usual load bearing activities during the recovery period following surgical operation.