Distal radius microstructure and finite element bone strain are related to site-specific mechanical loading and areal bone mineral density in premenopausal women

Abstract

While weight-bearing and resistive exercise modestly increases aBMD, the precise relationship between physical activity and bone microstructure, and strain in humans is not known. Previously, we established a voluntary upper-extremity loading model that assigns a person's target force based on their subject-specific, continuum FE-estimated radius bone strain. Here, our purpose was to quantify the inter-individual variability in radius microstructure and FE-estimated strain explained by site-specific mechanical loading history, and to determine whether variability in strain is captured by aBMD, a clinically relevant measure of bone density and fracture risk. Seventy-two women aged 21–40 were included in this cross-sectional analysis. High resolution peripheral quantitative computed tomography (HRpQCT) was used to measure macro- and micro-structure in the distal radius. Mean energy equivalent strain in the distal radius was calculated from continuum finite element models generated from clinical resolution CT images of the forearm. Areal BMD was used in a nonlinear regression model to predict FE strain. Hierarchical linear regression models were used to assess the predictive capability of intrinsic (age, height) and modifiable (body mass, grip strength, physical activity) predictors. Fifty-one percent of the variability in FE bone strain was explained by its relationship with aBMD, with higher density predicting lower strains. Age and height explained up to 31.6% of the variance in microstructural parameters. Body mass explained 9.1% and 10.0% of the variance in aBMD and bone strain, respectively, with higher body mass indicative of greater density. Overall, results suggest that meaningful differences in bone structure and strain can be predicted by subject characteristics.

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

“…The compressive force applied during this simple task is measured using a uniaxial load cell and simulated using a CT-based FE model of the radius, scaphoid and lunate. We have shown that among premenopausal women with normal bone mineral density (T-score [−2.5,1.0]), bone strain, which stimulates bone adaptation, is highly variable even when the same external force is applied to the hand ( Figure 3 ) [ 80 ]. We believe that in the future, exercise interventions would be more successful if individual differences in anatomy were considered, to generate specific bone strains.…”

Dominant and nondominant distal radius microstructure: Predictors of asymmetry and effects of a unilateral mechanical loading intervention

“…( Tsuji et al, 1995 )). We previously reported that nondominant distal radius cross-sectional area was positively correlated with age, height, and grip strength in a large subset of this cohort ( Mancuso et al, 2018 ). Here, we confirm that these relationships are similar in both the dominant and nondominant forearms.…”

“…A previous theoretical study suggested that a 10% increase in peak bone mass would result in an additional 13 years of osteoporosis-free life ( Hernandez et al, 2003 ). We recently showed that a 1 SD (11%) increase in areal bone mineral density (aBMD) at the distal radius was associated with a 20% increase in bone stiffness ( Mancuso et al, 2018 ). Twenty to 40% of peak bone mass is modifiable through lifestyle factors ( Weaver et al, 2016 ) including sports participation and other bone-loading physical activity.…”

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

“…The compressive force applied during this simple task is measured using a uniaxial load cell and simulated using a CT-based FE model of the radius, scaphoid and lunate. We have shown that among premenopausal women with normal bone mineral density (T-score [-2.5,1.0]), bone strain, which stimulates bone adaptation, is highly variable even when the same external force is applied to the hand (Figure 3) [71]. We believe that in the future, exercise interventions would be more successful if individual differences in anatomy were considered, to generate specific bone strains.…”