Femoral Neck bmd 1.6 1.4 1.2 0.8 06 0.4 20 60 80 100 Age(Years)
Femoral Neck BMD Femoral Neck BMD 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 20 40 60 80 100 Age (Years) BMD (g/cm2 )
Looking at the details Why do bones get less dense as we age? a Does this necessarily mean that bones are getting weaker? a Why do astronauts lose bone Z Are their bones getting weaker? a What factors are common between aging and microgravity and how do they differ?
Looking at the details Looking at the details Why do bones get less dense as we age? Why do bones get less dense as we age? Does this necessarily mean that bones are Does this necessarily mean that bones are getting weaker? getting weaker? Why do astronauts lose bone? Why do astronauts lose bone? Are their bones getting weaker? Are their bones getting weaker? What factors are common between aging What factors are common between aging and microgravity microgravity and how do they differ? and how do they differ?
Reduced Bone Strength Is an Engineering Problem Possible reasons 1. The material is less able to withstand coaaing stresses Or 2. The structure is altered to increase loading stresses
Reduced Bone Strength Reduced Bone Strength is an Engineering Problem is an Engineering Problem Possible reasons: Possible reasons: 1. The material is less able to withstand 1. The material is less able to withstand loading stresses loading stresses Or 2. The structure is altered to increase loading 2. The structure is altered to increase loading stresses stresses
Structure vS, Material Properties a Evidence exists that bone material strength declines with age but effect disappears when corrected fo porosity No good evidence that space-flight influences material properties a (no reliable way to measure in vivo anyway) a Without question bone structure changes with age and as a result of space -flight
Structure vs. Material Properties Structure vs. Material Properties Evidence exists that bone material strength declines Evidence exists that bone material strength declines with age but effect disappears when corrected for with age but effect disappears when corrected for porosity porosity No good evidence that space No good evidence that space -flight influences flight influences material properties material properties (no reliable way to measure (no reliable way to measure in vivo in vivo anyway) anyway) Without question Without question bone structure changes with age bone structure changes with age and as a result of space and as a result of space -flight
An engineering perspective Long bones act as inefficient levers, with actions due to muscle forces Greatest mechanical stresses are in bending and torsion
An engineering perspective An engineering perspective Long bones act as inefficient levers, Long bones act as inefficient levers, with actions due to muscle forces with actions due to muscle forces Greatest mechanical stresses are in Greatest mechanical stresses are in bending and torsion bending and torsion