Mechanostat - Modeling and Remodeling

Modeling and Remodeling

Frost defined four regions of elastic bone deformation which result in different consequences on the control loop:

• Disuse:
  Strain < circa 800μStrain: Remodeling (bone adaptation and bone repair) Bone mass and bone strength is reduced.
• Adapted State:
  strain between ca. 800μStrain and ca. 1500μStrain: Remodeling (bone repair) Bone mass and bone strength stays constant (homeostasis: bone resorption=bone formation)
• Overload:
  Strain > circa 1500μStrain: Modeling (bone growth) bone mass and bone strength is increased
• Fracture:
  Strain > circa 15000μStrain: maximum elastically deformation exceeded - bone fracture.

According to this a typical bone, e.g. the tibia has a security margin of about 5 to 7 between typical load (2000 to 3000 μStrain) and fracture load (about 15000μStrain).