Does bone design intend to minimize fatigue failures? A case for the affirmative.
Threshold strain ranges help to control the ability of modeling to increase bone strength and "mass" and the ability of remodeling to conserve or decrease them. Whether expressed as strains or stresses, the probable remodeling threshold of bone (MESr) lies below its modeling threshold (MESm), which lies below its operational microdamage threshold (MESp), which lies well below its ultimate strength (Fx). Given normal modeling and remodeling potentials, that arrangement should tend to cause whole-bone strength and stiffness to keep typical peak bone strains ("E") from voluntary activities from exceeding bone's modeling threshold and therefore from reaching its microdamage threshold. Satisfying that laddered "MESr < "E" < MESm << MESp <<< Fx" arrangement should minimize fatigue failures of bones, which might be at least one purpose of normal bone design. That arrangement would have practical implications that include, in part, the following. (A) It could make healthy young adult bones about six times stronger than needed for the largest voluntary loads they usually carry. (B) It suggests a biomechanical pathogenesis for different kinds of osteoporosis. (C) It suggests design criteria that load-bearing bone implants and endoprostheses should satisfy to endure their voluntary mechanical usage. (D) It also suggests features that future models of mechanical loading effects on bone strength, architecture, and "mass" might incorporate.
Frost
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Department of Orthopaedic Surgery, Southern Colorado Clinic, Pueblo 81008-9000, USA.
D001842:Bone and Bones / Q000502:physiology*; D006801:Humans; D008954:Models, Biological