Article

Annals of Biomedical Engineering

, Volume 31, Issue 1, pp 12-20

Adaptations of Trabecular Bone to Low Magnitude Vibrations Result in More Uniform Stress and Strain Under Load

  • Stefan JudexAffiliated withDepartment of Biomedical Engineering, State University of New York at Stony Brook
  • , Steve BoydAffiliated withInstitute for Biomedical Engineering, Swiss Federal Institute of Technology (ETH) and University Zürich
  • , Yi-Xian QinAffiliated withDepartment of Biomedical Engineering, State University of New York at Stony Brook
  • , Simon TurnerAffiliated withDepartment of Clinical Sciences, Colorado State University
  • , Kenny YeAffiliated withDepartment of Applied Mathematics and Statistics, State University of New York at Stony Brook
  • , Ralph MüllerAffiliated withInstitute for Biomedical Engineering, Swiss Federal Institute of Technology (ETH) and University Zürich
  • , Clinton RubinAffiliated withDepartment of Biomedical Engineering, State University of New York at Stony Brook

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Abstract

Extremely low magnitude mechanical stimuli (<10 microstrain) induced at high frequencies are anabolic to trabecular bone. Here, we used finite element (FE) modeling to investigate the mechanical implications of a one year mechanical intervention. Adult female sheep stood with their hindlimbs either on a vibrating plate (30 Hz, 0.3 g) for 20 min/d, 5 d/wk or on an inactive plate. Microcomputed tomography data of 1 cm bone cubes extracted from the medial femoral condyles were transformed into FE meshes. Simulated compressive loads applied to the trabecular meshes in the three orthogonal directions indicated that the low level mechanical intervention significantly increased the apparent trabecular tissue stiffness of the femoral condyle in the longitudinal (+17%, p < 0.02), anterior–posterior (+29%, p < 0.01), and medial-lateral (+37%, p < 0.01) direction, thus reducing apparent strain magnitudes for a given applied load. For a given apparent input strain (or stress), the resultant stresses and strains within trabeculae were more uniformly distributed in the off-axis loading directions in cubes of mechanically loaded sheep. These data suggest that trabecular bone responds to low level mechanical loads with intricate adaptations beyond a simple reduction in apparent strain magnitude, producing a structure that is stiffer and less prone to fracture for a given load. © 2003 Biomedical Engineering Society.

Bone adaptation Mechanical stimuli Mechanical strain and stress Mechanical properties Finite element modeling Bone formation Osteoporosis Noninvasive