Simplified Boundary Conditions Alter Cortical-trabecular Load Sharing at the Distal Radius; A Multiscale Finite Element Analysis

High-resolution peripheral quantitative computed tomography (HR-pQCT) derived micro-finite element (FE) modeling is used to evaluate mechanical behavior at the distal radius microstructure. However, these analyses typically simulate non-physiologic simplified platen-compression boundary conditions on a small section of the distal radius. Cortical and trabecular regions contribute uniquely to distal radius mechanical behavior, and various factors affect these regions distinctly. Generalized strength predictions from standardized platen-compression analyses may not adequately capture region specific responses in bone. Our goal was to compare load sharing within the cortical-trabecular compartments between the standardized platen-compression BC simulations, and physiologic BC simulations using a validated multiscale approach. Clinical- and high-resolution images were acquired from nine cadaveric forearm specimens using an HR-pQCT scanner. Multiscale FE models simulating physiologic BCs, and micro-FE only models simulating platen-compression BCs were created for each specimen. Cortical and trabecular loads (N) along the length of the distal radius micro-FE section were compared between BCs using correlations. Principal strain distributions were also compared quantitatively. Cortical and trabecular loads from the platen-compression BC simulations were strongly correlated to the physiologic BC simulations. However, a 30% difference in cortical loads distally, and a 53% difference in trabecular loads proximally was observed under platen BC simulations. Also, distribution of principal strains was clearly different. Our data indicated that platen-compression BC simulations alter cortical-trabecular load sharing. Therefore, results from these analyses should be interpreted in the appropriate mechanical context for clinical evaluations of normal and pathologic mechanical behavior at the distal radius.