Bone Mass Is Preserved and Cancellous Architecture Altered Due to Cyclic Loading of the Mouse Tibia After Orchidectomy

Authors

  • J Christopher Fritton,

    1. Field of Biomedical Engineering, Cornell University, Ithaca, New York, USA
    2. Laboratory for Biomedical Mechanics and Materials, Research Division, Hospital for Special Surgery, New York, New York, USA
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  • Elizabeth R Myers,

    1. Laboratory for Biomedical Mechanics and Materials, Research Division, Hospital for Special Surgery, New York, New York, USA
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  • Timothy M Wright,

    1. Field of Biomedical Engineering, Cornell University, Ithaca, New York, USA
    2. Laboratory for Biomedical Mechanics and Materials, Research Division, Hospital for Special Surgery, New York, New York, USA
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  • Marjolein CH van der Meulen PhD

    Corresponding author
    1. Field of Biomedical Engineering, Cornell University, Ithaca, New York, USA
    2. Laboratory for Biomedical Mechanics and Materials, Research Division, Hospital for Special Surgery, New York, New York, USA
    3. Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York, USA
    • Sibley School of Mechanical and Aerospace Engineering, Cornell University, 219 Upson Hall, Ithaca, NY 14853, USA
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  • This work was partially presented at the Summer Bioengineering Conference of the American Society of Mechanical Engineers, June 22–26, 2005, Vail, Colorado, USA.

  • The authors state that they have no conflicts of interest.

Abstract

Introduction: The study of adaptation to mechanical loading under osteopenic conditions is relevant to the development of osteoporotic fracture prevention strategies. We previously showed that loading increased cancellous bone volume fraction and trabecular thickness in normal male mice. In this study, we tested the hypothesis that cyclic mechanical loading of the mouse tibia inhibits orchidectomy (ORX)-associated cancellous bone loss.

Materials and Methods: Ten-week-old male C57BL/6 mice had in vivo cyclic axial compressive loads applied to one tibia every day, 5 d/wk, for 6 wk after ORX or sham operation. Adaptation of proximal cancellous and diaphyseal cortical bone was characterized by μCT and dynamic histomorphometry. Comparisons were made between loaded and nonloaded contralateral limbs and between the limbs of ORX (n = 10), sham (n = 11), and basal (n = 12) groups and tested by two-factor ANOVA with interaction.

Results: Cyclic loading inhibited bone loss after ORX, maintaining absolute bone mass at age-matched sham levels. Relative to sham, ORX resulted in significant loss of cancellous bone volume fraction (−78%) and trabecular number (−35%), increased trabecular separation (67%), no change in trabecular thickness, and smaller loss of diaphyseal cortical properties, consistent with other studies. Proximal cancellous bone volume fraction was greater with loading (ORX: 290%, sham: 68%) than in contralateral nonloaded tibias. Furthermore, trabeculae thickened with loading (ORX: 108%, sham: 48%). Dynamic cancellous bone histomorphometry indicated that loading was associated with greater mineral apposition rates (ORX: 32%, sham: 12%) and smaller percent mineralizing surfaces (ORX: −47%, sham: −39%) in the final week. Loading resulted in greater BMC (ORX: 21%, sham: 15%) and maximum moment of inertia (ORX: 39%, sham: 24%) at the cortical midshaft.

Conclusions: This study shows that cancellous bone mass loss can be prevented by mechanical loading after hormonal compromise and supports further exploration of nonpharmacologic measures to prevent rapid-onset osteopenia and associated fractures.

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