Investigation into the correlation between viscoelastic properties of fingernails and osteoporosis

A clear link between the mechanical properties of nail keratin and bone health is expected, but missing. Viscoelastic properties are one of the prime factors governing the mechanical properties of polymers. Fingernails, which are made of organic protein keratin, are fundamentally polymeric in nature and investigation into their viscoelastic properties is necessary to characterize their mechanical properties. In case of osteoporosis, organic mineral phases of bone are affected. Since the nail keratin and bone collagen share the need for protein sulphation and disulphide bond formation, any disorder in keratin synthesis could be related to the disorder in collagen synthesis. In the current work, instrumented nanoindentation is used to characterize the viscoelastic properties of nails of "healthy" vis-a-vis osteoporotic patients. In this preliminary investigation, qualitative differences have been established between the healthy and osteoporotic fingernails. These manifest as differences in the creep response. Furthermore it is also found that the point-to-point variations in individual fingernails are less than the differences between healthy and osteoporotic fingernails. The qualitative analysis of nanoindentation data requires detailed viscoelastic finite element modeling in conjunction with inverse analysis. The application of inverse analysis significantly reduces the amount of computation since FEM is only used to generate a parametric reference database.