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Research Papers

Short-Term Bone Formation is Greatest Within High Strain Regions of the Human Distal Radius: A Prospective Pilot Study

[+] Author and Article Information
Varun A. Bhatia

Cardiac Rhythm and Heart Failure,
Medtronic, Inc.,
Mounds View, MN, 55112

W. Brent Edwards

Human Performance Laboratory,
Faculty of Kinesiology,
University of Calgary,
Calgary, AB T2N 1N4, Canada

Joshua E. Johnson

Department of Biomedical Engineering,
Worcester Polytechnic Institute,
100 Institute Road,
Worcester, MA 01609

Karen L. Troy

Assistant Professor
Department of Biomedical Engineering,
Worcester Polytechnic Institute,
100 Institute Road,
Worcester, MA 01609
e-mail: ktroy@wpi.edu

1Corresponding author.

Manuscript received May 21, 2014; final manuscript received October 8, 2014; accepted manuscript posted October 20, 2014; published online December 10, 2014. Assoc. Editor: Ara Nazarian.

J Biomech Eng 137(1), 011001 (Jan 01, 2015) Paper No: BIO-14-1219; doi: 10.1115/1.4028847 History: Received May 21, 2014; Revised October 08, 2014; Accepted October 20, 2014; Online December 10, 2014

Bone adaptation is understood to be driven by mechanical strains acting on the bone as a result of some mechanical stimuli. Although the strain/adaptation relation has been extensively researched using in vivo animal loading models, it has not been studied in humans, likely due to difficulties in quantifying bone strains and adaptation in living humans. Our purpose was to examine the relationship between bone strain and changes in bone mineral parameters at the local level. Serial computed tomography (CT) scans were used to calculate 14 week changes in bone mineral parameters at the distal radius for 23 women participating in a cyclic in vivo loading protocol (leaning onto the palm of the hand), and 12 women acting as controls. Strains were calculated at the distal radius during the task using validated finite element (FE) modeling techniques. Twelve subregions of interest were selected and analyzed to test the strain/adaptation relation at the local level. A positive relationship between mean energy equivalent strain and percent change in bone mineral density (BMD) (slope = 0.96%/1000 με, p < 0.05) was observed within experimental, but not control subjects. When subregion strains were grouped by quartile, significant slopes for quartile versus bone mineral content (BMC) (0.24%/quartile) and BMD (0.28%/quartile) were observed. Increases in BMC and BMD were greatest in the highest-strain quartile (energy equivalent strain > 539 με). The data demonstrate preliminary prospective evidence of a local strain/adaptation relationship within human bone. These methods are a first step toward facilitating the development of personalized exercise prescriptions for maintaining and improving bone health.

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Figures

Grahic Jump Location
Fig. 1

(a) Targeted loading protocol, sagittal view, (b) FE model (cartilage removed) with boundary conditions shown, palmar view. Contours display minimum (compressive) principle strain at the periosteal surface during loading for an example subject.

Grahic Jump Location
Fig. 2

Three 1 cm slices proximal to the subchondral plate, each divided into quadrants about their respective centroid. The distal-most slice includes the entire 9.375 mm UD section. The 12 subregions used for local analysis consisted of the 4 quadrants × 3 slices.

Grahic Jump Location
Fig. 3

Energy equivalent strain versus percent change in BMD for all subregions of subjects in the experimental group. Black diamonds and error bars represent the quartile means and standard deviations, and dashed vertical lines show the strain quartile divisions. Regression slope: 0.28%/quartile.

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