title: Mechanical and structural properties of bone in non-critical and critical healing in rat.
abstract: A fracture in bone results in a dramatic change of mechanical loading conditions at the site of injury. Usually, bone injuries heal normally but with increasing fracture gaps, healing is retarded, eventually leading to non-unions. The clinical situation of these two processes with different outcomes is well described. However, the exact relation between the mechanical environment and characteristics of the tissues at all levels of structural hierarchy remains unclear. Here we studied the differences in material formation of non-critical (1mm) and critical (5mm gap) healing. We employed a rat osteotomy model to explore bone material structure depending upon the different mechanical conditions. In both cases, primary bone formation was followed by secondary bone deposition with mineral particle sizes changing from on average short and thick to long and thin particles. Bony bridging occurred at first in the endosteal callus and the nanostructure and microstructure developed towards cortical ordered material organization. In contrast, in critical healing, instead of bridging, a marrow cavity closure was formed endosteal, exhibiting tissue structure oriented along the curvature and a periosteal callus with less mature material structure. The two healing processes separated between 4 and 6 weeks post-osteotomy. The outcome of healing was determined by the varied geometrical conditions in critical and non-critical healing, inducing completely different mechanical situations.
authors.affiliation: Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Research Campus Golm, 14424 Potsdam, Germany; Berlin-Brandenburg School for Regenerative Therapies (BSRT), Charité - Universitätsmedizin Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Hoerth
authors.affiliation: Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Research Campus Golm, 14424 Potsdam, Germany.
authors.forename: Britta M
authors.initials: BM
authors.lastname: Seidt
authors.affiliation: Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Research Campus Golm, 14424 Potsdam, Germany.
authors.forename: Miheer
authors.initials: M
authors.lastname: Shah
authors.affiliation: Berlin-Brandenburg School for Regenerative Therapies (BSRT), Charité - Universitätsmedizin Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany; Julius Wolff Institute & Center for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Carolin
authors.initials: C
authors.lastname: Schwarz
authors.affiliation: Julius Wolff Institute & Center for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Bettina M
authors.initials: BM
authors.lastname: Willie
authors.affiliation: Julius Wolff Institute & Center for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Georg N
authors.initials: GN
authors.lastname: Duda
authors.affiliation: Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Research Campus Golm, 14424 Potsdam, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Fratzl
authors.affiliation: Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Research Campus Golm, 14424 Potsdam, Germany. Electronic address: Wolfgang.Wagermaier@mpikg.mpg.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wagermaier
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001842:Bone and Bones / Q000473:pathology* / Q000503:physiopathology*; D002113:Calcification, Physiologic; D003460:Crystallization; D055119:Elastic Modulus; D006244:Hardness; D053758:Nanoparticles / Q000737:chemistry; D017207:Rats, Sprague-Dawley; D053838:Scattering, Small Angle; D017356:Synchrotrons; D014945:Wound Healing; D014961:X-Ray Diffraction
keywords: Bone healing; Critical size defect; Mechanical properties; Nanostructure; X-ray scattering