Heterogeneous Spatial and Strength Adaptation of the Proximal Femur to Physical Activity: A Within-Subject Controlled Cross-Sectional Study

Abstract

Physical activity (PA) enhances proximal femur bone mass, as assessed using projectional imaging techniques. However, these techniques average data over large volumes, obscuring spatially heterogeneous adaptations. The current study used quantitative computed tomography, statistical parameter mapping, and subject‐specific finite element (FE) modeling to explore spatial adaptation of the proximal femur to PA. In particular, we were interested in adaptation occurring at the superior femoral neck and improving strength under loading from a fall onto the greater trochanter. High/long jump athletes (n = 16) and baseball pitchers (n = 16) were utilized as within‐subject controlled models as they preferentially load their take‐off leg and leg contralateral to their throwing arm, respectively. Controls (n = 15) were included but did not show any dominant‐to‐nondominant (D‐to‐ND) leg differences. Jumping athletes showed some D‐to‐ND leg differences but less than pitchers. Pitchers had 5.8% (95% confidence interval [CI] 3.9%–7.6%) D‐to‐ND leg differences in total hip volumetric bone mineral density (vBMD), with increased vBMD in the cortical compartment of the femoral neck and trochanteric cortical and trabecular compartments. Voxel‐based morphometry analyses and cortical bone mapping showed pitchers had D‐to‐ND leg differences within the regions of the primary compressive trabeculae, inferior femoral neck, and greater trochanter but not the superior femoral neck. FE modeling revealed pitchers had 4.1% (95% CI 1.4%–6.7%) D‐to‐ND leg differences in ultimate strength under single‐leg stance loading but no differences in ultimate strength to a fall onto the greater trochanter. These data indicate the asymmetrical loading associated with baseball pitching induces proximal femur adaptation in regions associated with weight bearing and muscle contractile forces and increases strength under single‐leg stance loading. However, there were no benefits evident at the superior femoral neck and no measurable improvement in ultimate strength to common injurious loading during aging (ie, fall onto the greater trochanter), raising questions as to how to better target these variables with PA. © 2019 American Society for Bone and Mineral Research.

Hip load capacity and yield load in men and women of all ages

“…Therefore, decreases in the yield load of an individual may be an early indicator of declining load capacity and future increases in hip fracture risk. Fall yield load may also be useful for evaluating interventions that affect trabecular bone, such as exercise [34][35].…”

Post-operative fracture risk assessment following tumor curettage in the distal femur: a hybrid in vitro and in silico biomechanical approach

“…www.nature.com/scientificreports/ The distortion energy failure theory applied in our study has also been widely used since its validation as a robust theory for bone failure when using elastic-plastic and isotropic material properties for bone 16,33,43,54 . Warden et al 43 calculated femoral strength considering heterogeneous and non-linear post-yield material properties under a compressive load that was applied by an incremental displacement on the femoral head. They computed the element stress and strain, using individual element's stress-strain relationship, similar to the relations used in this study, in conjunction with the von Mises yield criterion 43 .…”

“…However, the Drucker–Prager yield criterion 55 , which is an approximation to the Mohr–Coulomb law and a modification of the Von Mises yield criterion, is applied in some studies modelling bone as a brittle material with isotropic material properties 52 , 53 . The distortion energy failure theory applied in our study has also been widely used since its validation as a robust theory for bone failure when using elastic–plastic and isotropic material properties for bone 16 , 33 , 43 , 54 . Warden et al 43 calculated femoral strength considering heterogeneous and non-linear post-yield material properties under a compressive load that was applied by an incremental displacement on the femoral head.…”

“…Warden et al 43 calculated femoral strength considering heterogeneous and non-linear post-yield material properties under a compressive load that was applied by an incremental displacement on the femoral head. They computed the element stress and strain, using individual element’s stress–strain relationship, similar to the relations used in this study, in conjunction with the von Mises yield criterion 43 . Most recently, a study measured hip load capacity using elastic–plastic and isotropic modeling of bone in conjunction with the distortion energy yield criterion 54 .…”

“…The sum of the reaction forces of the nodes (where the compressive load was applied) versus their average displacement was plotted, and the maximum force on the curve was considered as the FE predicted fracture load (F FE ). Finite element analyses were performed in ABAQUS (v6.13-4, Dassault Systèmes), using distortion energy failure theory, as a validated bone failure theory 42 , 43 .…”