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Bones Adaptation

Bones Adaptation. Overuse: Exercise. Bone Adaptation. Disuse: bone mass is reduced. Aging and Bone. Is it possible that we can compensate to age related changes in decreased bone density by changing geometry? Hip fractures. Bone Biology. Cells in fibrous organic matrix. Collagen. Cells.

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Bones Adaptation

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  1. Bones Adaptation • Overuse: Exercise

  2. Bone Adaptation • Disuse: bone mass is reduced

  3. Aging and Bone • Is it possible that we can compensate to age related changes in decreased bone density by changing geometry? • Hip fractures

  4. Bone Biology • Cells in fibrous organic matrix

  5. Collagen

  6. Cells • Osteoblasts- • Osteoclasts- • Osteocytes-

  7. Bone classification • Cortical Bone • Trabecular Bone

  8. X-section of Bone

  9. Bone architecture

  10. Trabecular Bone (aging)

  11. Review???? • Deformation of an axially loaded long rod? F F

  12. Review

  13. Bone Shape • Since bone isn’t straight, the compressive loads also cause bending

  14. Bone stresses • Bending an I beam, • But... Long bones are subjected to???

  15. Bone Loading • Axial compressive load • Bending (multiple directions) • Torsion • So, why is the bone hollow?

  16. Bone Loading

  17. Bone Loading-Aging • Elderly increase both surfaces • Appear that elderly bones see because of geometry, but their is higher, so material properties.

  18. Bone-Aging • Change in geometry is not enough to make up for decreased material properties • And--- they have a decline in their “senses” as well with age-so less stable and fall more often.

  19. Bone-Torsion • Angle of Twist in a circular bar subjected to a known torque, T?

  20. Aging σult men Women-due to estrogen age Estrogen inhibits bone resorption

  21. Material Prop. of Cortical Bone • Rate of loading (strain rate, ε) • Normal activities (walking)

  22. Material Prop. of Cortical Bone • Rate of loading • Orientation of microstructure w/r/t loading direction

  23. Material Prop. Of Trabecular Bone Modulus trabecular bone~50MPa, tensile strength ~3MPa

  24. Material Prop. Of Trabecular Bone • Yielding occurs as trabeculae fracture *** Example 6 in book ***

  25. Age-geometry changes • Men compensate more than women by changing their cortical bone diaphyseal geometry to counter the decrease in strength *** Examples 8 in book*****

  26. Fracture Risk/Prediction • * when we finish this section, hopefully we will understand why women fracture hip more often • Yes, increased hip span-which relates to increased moment arm out to muscles, so slight increases in contact forces in hip---but….. You don’t fracture your hip due to contact forces while walking.

  27. Fracture Risk/Prediction • By definition, Fracture:.

  28. Fracture Risk/Prediction • Load-Bearing capacity: • Determining bone fracture:

  29. Fracture Risk/Prediction • hip fractures occur during a fall • Fracture in bone of hip • Fewer than 2% of falls in elderly result in hip fracture

  30. Fracture Risk/Prevention • Factors related to the tendency to fall • not study in this class • Fall severity (i.e. mag. and dir. of loads) • Strength of femur

  31. Fall severity • Fall to the side rather than other direction • Increase in potential energy • Arm strength to break fall • Muscle activity • Soft tissue thickness over hip

  32. Influences strength of proximal femur • Material properties • Size (total amount) • Shape (spatial distribution, I,J)

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