Contribution of In Vivo Structural Measurements and Load/Strength Ratios to the Determination of Forearm Fracture Risk in Postmenopausal Women

Authors

  • L Joseph Melton III MD,

    Corresponding author
    1. Division of Epidemiology, Department of Health Sciences Research, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
    2. Division of Endocrinology, Metabolism, and Nutrition, Department of Internal Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
    • Division of Epidemiology, Department of Health Sciences Research, Mayo Clinic, 200 First Street Southwest, Rochester, MN 55905, USA
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    • Dr Melton has served as a speaker for Amgen, Merck & Co., and Procter & Gamble. All other authors state that they have no conflicts of interest.

  • B Lawrence Riggs,

    1. Division of Endocrinology, Metabolism, and Nutrition, Department of Internal Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
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  • G Harry van Lenthe,

    1. Institute for Biomechanics, ETH Zurich, Zurich, Switzerland
    2. Division of Biomechanics and Engineering Design, K.U. Leuven, Leuven, Belgium
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  • Sara J Achenbach,

    1. Division of Biostatistics, Department of Health Sciences Research, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
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  • Ralph Müller,

    1. Institute for Biomechanics, ETH Zurich, Zurich, Switzerland
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  • Mary L Bouxsein,

    1. Orthopedic Biomechanics Laboratory, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
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  • Shreyasee Amin,

    1. Division of Rheumatology, Department of Internal Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
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  • Elizabeth J Atkinson,

    1. Division of Biostatistics, Department of Health Sciences Research, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
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  • Sundeep Khosla

    1. Division of Endocrinology, Metabolism, and Nutrition, Department of Internal Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
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Abstract

Bone structure, strength, and load-strength ratios contribute to forearm fracture risk independently of areal BMD.

Introduction: Technological and conceptual advances provide new opportunities for evaluating the contributions of bone density, structure, and strength to the pathogenesis of distal forearm fractures.

Materials and Methods: From an age-stratified random sample of Rochester, MN, women, we compared 18 with a distal forearm fracture (cases) to 18 age-matched women with no osteoporotic fracture (controls). High-resolution pQCT was used to assess volumetric BMD (vBMD), geometry, and microstructure at the ultradistal radius, the site of Colles' fractures. Failure loads in the radius were estimated from microfinite element (μFE) models derived from pQCT. Differences between case and control women were assessed, and the risk of fracture associated with each variable was estimated by logistic regression analysis.

Results: Given similar heights, estimated loading in a fall on the outstretched arm was the same in cases and controls. However, women with forearm fractures had inferior vBMD, geometry, microstructure, and estimated bone strength. Relative risks for the strongest determinant of fracture in each of the five main variable categories were as follows: BMD (total vBMD: OR per SD change, 4.2; 95% CI, 1.4–12), geometry (cortical thickness: OR, 4.0; 95% CI, 1.4–11), microstructure (trabecular number: OR, 2.3; 95% CI, 1.02–5.1), and strength (axial rigidity: OR, 3.8; 95% CI, 1.4–10); the factor-of-risk (fall load/μFE failure load) was 24% greater (worse) in cases (OR, 3.0; 95% CI, 1.2–7.5). Areas under ROC curves ranged from 0.72 to 0.82 for these parameters.

Conclusions: Bone geometry, microstructure, and strength contribute to forearm fractures, as does BMD, and these additional determinants of risk promise greater insights into fracture pathogenesis.

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