A Comprehensive Triad Analysis of Biphasic Plate Mechanics: In Vivo, In Vitro, and In Silico Perspectives
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The treatment of distal femur fractures is a lengthy process. The gold standard is fixation using plate osteosynthesis; however, these systems are susceptible to excessive loading. The new biphasic plate promises high construct stiffness. Relevant mechanical conditions create effects (flex and rigid phase) which have a positive influence on healing [1,2]. As this represents a novel implant design, only a few studies have investigated it so far, particularly with respect to human cadaveric specimens and in vivo patient-specific cases. Therefore, this study aims to investigate the biphasic behavior using in vitro, in silico, and in vivo methodologies (see figure 1) concerning stress distributions under realistic boundary conditions. A human cadaveric specimen was used to induce an osteotomy to shape a transverse fracture. This specimen was tested under quasi-static loading until both phases (flex and rigid) were captured visually. A strain measurement system (“Fracture Monitor”, AO Foundation, Davos, Switzerland) and force sensors measured upcoming forces and plate’s strain. Accordingly, a finite element simulation was done, recreating the experimental results. Biomechanical simulations were performed on patient-specific computational models (4 cases) using forces of the gait cycle from patients measuring realistic boundary conditions. The experimental measurements provided values for validating the subsequent biomechanical simulations and captured both phases of the plate. Under axial loading, the stresses are distributed centrally; while in patient-specific cases, the stress pattern changes markedly, with maximum stresses concentrating along the lateral side of the plate. The triad of in vitro, in silico, and in vivo approaches enables a comprehensive investigation across all relevant levels, even though each method has inherent limitations. It is precisely this integrated triad that allows the results to be interpreted in a coherent and clinically meaningful way.
