title: Predicting surface strains at the human distal radius during an in vivo loading task--finite element model validation and application.
abstract: Bone strains resulting from physical activity are thought to be a primary driver of bone adaptation, but cannot be directly noninvasively measured. Because bone adapts nonuniformly, physical activity may make an important independent structural contribution to bone strength that is independent of bone mass and density. Our objective was to create and validate methods for subject-specific finite element (FE) model generation that would accurately predict the surface strains experienced by the distal radius during an in vivo loading task, and to apply these methods to a group of 23 women aged 23-35 to examine variations in strain, bone mass and density, and physical activity. Four cadaveric specimens were experimentally tested and specimen-specific FE models were developed to accurately predict periosteal surface strains (root mean square error=16.3%). In the living subjects, when 300 N load was simulated, mean strains were significantly inversely correlated with BMC (r=-0.893), BMD (r=-0.892) and physical activity level (r=-0.470). Although the group of subjects was relatively homogenous, BMD varied by two-fold (range: 0.19-0.40 g/cm(3)) and mean energy-equivalent strain varied by almost six-fold (range: 226.79-1328.41 με) with a simulated 300 N load. In summary, we have validated methods for estimating surface strains in the distal radius that occur while leaning onto the palm of the hand. In our subjects, strain varied widely across individuals, and was inversely related to bone parameters that can be measured using clinical CT, and inversely related to physical activity history.
authors.affiliation: Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, United States.
authors.forename: Varun A
authors.initials: VA
authors.lastname: Bhatia
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.
authors.forename: W Brent
authors.initials: WB
authors.lastname: Edwards
authors.affiliation: Department of Biomedical Engineering, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609, United States. Electronic address: ktroy@wpi.edu.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Troy
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000369:Aged, 80 and over; D015519:Bone Density; D002102:Cadaver; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D008954:Models, Biological; D011884:Radius / Q000000981:diagnostic imaging / Q000502:physiology*; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed; D016474:Weight-Bearing; D014955:Wrist Joint; D055815:Young Adult
keywords: Bone; Bone adaptation; Cadaver testing; Finite element; Human; Physical activity; Strain gage