title: The Periosteal Bone Surface is Less Mechano-Responsive than the Endocortical.
abstract: Dynamic processes modify bone micro-structure to adapt to external loading and avoid mechanical failure. Age-related cortical bone loss is thought to occur because of increased endocortical resorption and reduced periosteal formation. Differences in the (re)modeling response to loading on both surfaces, however, are poorly understood. Combining in-vivo tibial loading, in-vivo micro-tomography and finite element analysis, remodeling in C57Bl/6J mice of three ages (10, 26, 78 week old) was analyzed to identify differences in mechano-responsiveness and its age-related change on the two cortical surfaces. Mechanical stimulation enhanced endocortical and periosteal formation and reduced endocortical resorption; a reduction in periosteal resorption was hardly possible since it was low, even without additional loading. Endocortically a greater mechano-responsiveness was identified, evident by a larger bone-forming surface and enhanced thickness of formed bone packets, which was not detected periosteally. Endocortical mechano-responsiveness was better conserved with age, since here adaptive response declined continuously with aging, whereas periosteally the main decay in formation response occurred already before adulthood. Higher endocortical mechano-responsiveness is not due to higher endocortical strains. Although it is clear structural adaptation varies between different bones in the skeleton, this study demonstrates that adaptation varies even at different sites within the same bone.
authors.affiliation: Julius Wolff Institute, Charité - Universitätsmedizin Berlin, Berlin Germany.|Continuum Biomechanics and Mechanobiology Research Group, Institute of Applied Mechanics, University of Stuttgart, Germany.
authors.forename: Annette I
authors.initials: AI
authors.lastname: Birkhold
authors.affiliation: Julius Wolff Institute, Charité - Universitätsmedizin Berlin, Berlin Germany.
authors.forename: Hajar
authors.initials: H
authors.lastname: Razi
authors.affiliation: Julius Wolff Institute, Charité - Universitätsmedizin Berlin, Berlin Germany.
authors.forename: Georg N
authors.initials: GN
authors.lastname: Duda
authors.affiliation: Max Planck Institute of Colloids and Interfaces, Potsdam, Department of Biomaterials, Germany.
authors.forename: Richard
authors.initials: R
authors.lastname: Weinkamer
authors.affiliation: Julius Wolff Institute, Charité - Universitätsmedizin Berlin, Berlin Germany.
authors.forename: Sara
authors.initials: S
authors.lastname: Checa
authors.affiliation: Julius Wolff Institute, Charité - Universitätsmedizin Berlin, Berlin Germany.|Research Centre, Shriners Hospital for Children-Canada, Department of Pediatric Surgery, McGill University, Montreal, Canada.
authors.forename: Bettina M
authors.initials: BM
authors.lastname: Willie
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001696:Biomechanical Phenomena; D001862:Bone Resorption / Q000000981:diagnostic imaging* / Q000209:etiology / Q000473:pathology; D020342:Finite Element Analysis; D051379:Mice; D008807:Mice, Inbred BALB C; D010521:Periosteum / Q000000981:diagnostic imaging* / Q000473:pathology; D013314:Stress, Mechanical; D013977:Tibia / Q000473:pathology; D055114:X-Ray Microtomography / Q000379:methods*