Dilatational band formation in bone

Atharva A. Poundarik, Tamim Diab, Grazyna E. Sroga, Ani Ural, Adele L. Boskey, Caren M. Gundberg, Deepak Vashishth

Research output: Contribution to journalArticlepeer-review

177 Scopus citations

Abstract

Toughening in hierarchically structured materials like bone arises from the arrangement of constituent material elements and their interactions. Unlike microcracking, which entails micrometer-level separation, there is no known evidence of fracture at the level of bone's nanostructure. Here, we show that the initiation of fracture occurs in bone at the nanometer scale by dilatational bands. Through fatigue and indentation tests and laser confocal, scanning electron, and atomic force microscopies on human and bovine bone specimens, we established that dilatational bands of the order of 100 nm form as ellipsoidal voids in between fused mineral aggregates and two adjacent proteins, osteocalcin (OC) and osteopontin (OPN). Laser microdissection and ELISA of bone microdamage support our claim that OC and OPN colocalize with dilatational bands. Fracture tests on bones from OC and/or OPN knockout mice (OC-/-, OPN -/-, OC-OPN-/-;-/-) confirm that these two proteins regulate dilatational band formation and bone matrix toughness. On the basis of these observations, we propose molecular deformation and fracture mechanics models, illustrating the role of OC and OPN in dilatational band formation, and predict that the nanometer scale of tissue organization, associated with dilatational bands, affects fracture at higher scales and determines fracture toughness of bone.

Original languageEnglish
Pages (from-to)19178-19183
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume109
Issue number47
DOIs
StatePublished - 20 Nov 2012
Externally publishedYes

Keywords

  • Diffuse damage
  • Energy dissipation
  • Noncollagenous proteins

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