Simplified boundary conditions alter cortical-trabecular load sharing at the distal radius; A multiscale finite element analysis

Abstract

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.

Exercise Early and Often: Effects of Physical Activity and Exercise on Women’s Bone Health

“…FE models are useful for estimating strains within the bone of a living person. However, we have shown that models that simulate platen compression, which often used to estimate bone strength, do not accurately replicate the strains that occur during physiologic loading [ 92 ]. If FE models based on these images are to be useful for predicting bone strain during an exercise, it is important to include accurate (physiological) boundary conditions [ 93 ].…”

Bone Mechanoregulation Allows Subject-Specific Load Estimation Based on Time-Lapsed Micro-CT and HR-pQCT in Vivo

“…Our results also show that using the simplified compressive boundary condition may be an acceptable choice when investigating trabecular bone mechanoregulation of the healthy human distal radius. However, Johnson and Troy (2018) have shown that this simplified compression boundary condition may alter cortical and trabecular loading sharing. Therefore, the authors caution that such a simplified boundary condition may not be adequate for future studies investigating cortical and trabecular bone mechanoregulation.…”

“…This suggests that only part of the bone structure may be load adapted. The actual in vivo load distribution might differ systematically from the homogeneous assumption in humans (Christen et al, 2016;Johnson and Troy, 2018) and mice (Christen et al, 2012). By modelling homogenised strain patterns, the conventional algorithm may reduce mechanical signal inhomogeneities that have been recognised as drivers for the mechanoregulated remodelling process in bone (Frost, 1987(Frost, , 2003.…”

Bone mechanoregulation allows subject-specific load estimation based on time-lapsed micro-CT and HR-pQCTin vivo

“…Our results also show that using the simplified compressive boundary condition may be an acceptable choice when investigating trabecular bone mechanoregulation the healthy human distal radius. However, Johnson and Troy (2018) have shown that this simplified compression boundary condition may alter cortical and trabecular loading sharing. Therefore, the authors caution that such a simplified boundary condition may not be adequate for future studies investigating cortical and trabecular bone mechanoregulation.…”

“…However, remaining signal inhomogeneity remained high, ranging between 20-67%, indicating that no homogenous tissue load could be found (Christen et al, 2012). This suggests that the actual in vivo load distribution might differ systematically from the homogeneous assumption in humans (Christen et al, 2016;Johnson and Troy, 2018) and mice (Christen et al, 2012). By modelling homogenised strain patterns, the conventional algorithm may reduce mechanical signal inhomogeneities that have been recognised as drivers for the mechanoregulated remodelling process in bone (Frost, 1987(Frost, , 2003.…”