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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
Bones Adaptation
  • Overuse: Exercise
bone adaptation
Bone Adaptation
  • Disuse: bone mass is reduced
aging and bone
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
Bone Biology
  • Cells in fibrous organic matrix
  • Osteoblasts-
  • Osteoclasts-
  • Osteocytes-
bone classification
Bone classification
  • Cortical Bone
  • Trabecular Bone
  • Deformation of an axially loaded long rod?



bone shape
Bone Shape
  • Since bone isn’t straight, the compressive loads also cause bending
bone stresses
Bone stresses
  • Bending an I beam,
  • But... Long bones are subjected to???
bone loading
Bone Loading
  • Axial compressive load
  • Bending (multiple directions)
  • Torsion
  • So, why is the bone hollow?
bone loading aging
Bone Loading-Aging
  • Elderly increase both surfaces
  • Appear that elderly bones see because of geometry, but their is higher, so material properties.
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.
bone torsion
  • Angle of Twist in a circular bar subjected to a known torque, T?



Women-due to estrogen


Estrogen inhibits bone resorption

material prop of cortical bone
Material Prop. of Cortical Bone
  • Rate of loading (strain rate, ε)
    • Normal activities (walking)
material prop of cortical bone1
Material Prop. of Cortical Bone
  • Rate of loading
  • Orientation of microstructure w/r/t loading direction
material prop of trabecular bone
Material Prop. Of Trabecular Bone

Modulus trabecular bone~50MPa, tensile strength ~3MPa

material prop of trabecular bone1
Material Prop. Of Trabecular Bone
  • Yielding occurs as trabeculae fracture

*** Example 6 in book ***

age geometry changes
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*****

fracture risk prediction
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.
fracture risk prediction1
Fracture Risk/Prediction
  • By definition, Fracture:.
fracture risk prediction2
Fracture Risk/Prediction
  • Load-Bearing capacity:
  • Determining bone fracture:
fracture risk prediction3
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
fracture risk prevention
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
fall severity
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
influences strength of proximal femur
Influences strength of proximal femur
  • Material properties
  • Size (total amount)
  • Shape (spatial distribution, I,J)