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Long-term ovariectomy decreases ovine compact bone viscoelasticity
C M Les1, J L Vance, G T Christopherson
1Department of Orthopaedic Surgery, Bone and Joint Center, Henry Ford Hospital, 2015 Benson Ford Education and Research Building, 2799 W. Grand Blvd., Detroit, MI 48202, USA. les@bjc.hfh.edu
Summary
Estrogen depletion significantly alters bone viscoelasticity, reducing bone strength and toughness. These changes in bone quality may not be detected by standard bone density scans.
Area of Science:
- Biomechanical Engineering
- Orthopedics
- Endocrinology
Background:
- Estrogen depletion is linked to increased fracture risk, but bone mineral density changes alone don't fully explain this.
- Bone quality, beyond density, likely plays a crucial role in fracture susceptibility.
Purpose of the Study:
- To investigate how estrogen depletion affects the viscoelastic properties of compact bone.
- To determine if changes in bone viscoelasticity contribute to increased fracture risk.
Main Methods:
- Ovine radius bone samples were used after three years of ovariectomy.
- Dynamic mechanical analysis (DMA) with low-amplitude 3-point bending was performed at 1-20 Hz.
- Viscoelastic storage modulus and loss tangent (damping) were measured.
Main Results:
- Ovariectomized animals showed a significant decrease (5.2%) in viscoelastic storage modulus at higher frequencies.
- The loss tangent (damping) decreased significantly (up to 83%) at high frequencies in ovariectomized animals.
- Anatomic variations in damping were enhanced by ovariectomy.
Conclusions:
- Estrogen depletion alters compact bone's viscoelastic properties, potentially reducing bone toughness and strength.
- These viscoelastic changes may contribute to fracture risk independently of bone mineral density.
- Current screening methods like DXA may not capture these crucial changes in bone quality.