title: In situ observation of fracture behavior of canine cortical bone under bending.
abstract: Cortical bone provides many important body functions and maintains the rigidness and elasticity of bone. A common failure mode for bone structure is fracture under a bending force. In the current study, the fracture behavior of canine cortical bone under three-point bending was observed in situ using an atomic force microscope (AFM), a scanning electron microscope (SEM), and an optical microscope to examine the fracture process in detail. Nanoindentation was carried out to determine the elastic modulus and hardness of different building blocks of the canine cortical bone. The results have shown that the special structure of Haversian systems has significant effects on directing crack propagation. Although Haversian systems contain previously believed weak points, and micro-cracks initiate within Haversian systems, our findings have demonstrated that macro-cracks typically form around the boundaries of Haversian systems, i.e. the cement lines. Micro-cracks that developed inside Haversian systems have the functions of absorbing and dissipating energy and slow down on expanding when interstitial tissue cannot hold any more pressure, then plastic deformation and fracture occur.
authors.affiliation: Department of Orthopaedics, Medical University of South Carolina, 96 Jonathan Lucas Street Suite 708 MSC 622, Charleston, SC 29425, United States; Department of Mechanical Engineering, University of South Carolina, 300 Main Street, Columbia, SC 29208, United States.
authors.forename: Zilan X
authors.initials: ZX
authors.lastname: Lin
authors.affiliation: Department of Mechanical Engineering, University of South Carolina, 300 Main Street, Columbia, SC 29208, United States.
authors.forename: Zhi-Hui
authors.initials: ZH
authors.lastname: Xu
authors.affiliation: Department of Orthopaedics, Medical University of South Carolina, 96 Jonathan Lucas Street Suite 708 MSC 622, Charleston, SC 29425, United States; Department of Orthopaedic Surgery, Southside Hospital, North Shore-LIJ Health System, 217 East Main Street, Bay Shore, NY 11706, United States.
authors.forename: Yuehuei H
authors.initials: YH
authors.lastname: An
authors.affiliation: Department of Mechanical Engineering, University of South Carolina, 300 Main Street, Columbia, SC 29208, United States; Department of Mechanical and Aerospace Engineering, University of Virginia, 122 Engineer's Way, Charlottesville, VA 22904, United States. Electronic address: xl3p@virginia.edu.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Li
mesh_terms: D000818:Animals; D001842:Bone and Bones; D004285:Dogs; D055119:Elastic Modulus; D050723:Fractures, Bone; D018625:Microscopy, Atomic Force; D013314:Stress, Mechanical
keywords: Cortical bone; Fracture behavior; Haversian system; Three point bending