title: Stress mapping of undamaged, strained, and failed regions of bone using Raman spectroscopy.
abstract: Stress differences via spectral shifts that arise among failed, strained, and undamaged regions of bone can be determined using Raman spectroscopy and double-notch specimens. A double-notch specimen is a model in which the early stages of fracture can be examined. At four-point bending, fracture occurs at one of the notches. Tissue near each notch is representative of bone in a state either directly before or after bone failure. Raman images are acquired among three regions: control, strained (root of unbroken notch), and failed (root of fractured notch). The center of gravities (CGs), a way to monitor wavenumber shifts, of the phosphate v(1) band are calculated. A PO(4) (-3) v(1) band shift most likely corresponds to a change in spacing between phosphate cations and anions. This spectral shift is converted into stress values using the dvdP coefficient, determined by applying known pressures/stresses and measuring the change in position of the PO(4) (-3) v(1) band. In comparison to control regions, the residual stress in strained and failed regions is significantly higher (p=0.0425 and p=0.0169, respectively). In strained regions, residual stress is concentrated near the corners of the unbroken notch, whereas in failed regions the high stresses are confined near the edge of the fracture.
authors.affiliation: University of Michigan, Department of Chemistry, 930 North University Avenue, Ann Arbor, Michigan 48109, USA.
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Dooley
authors.forename: Jordan
authors.initials: J
authors.lastname: McCormack
authors.forename: David P
authors.initials: DP
authors.lastname: Fyhrie
authors.forename: Michael D
authors.initials: MD
authors.lastname: Morris
mesh_terms: D000465:Algorithms; D000818:Animals; D055119:Elastic Modulus; D015775:Fractures, Stress / Q000175:diagnosis* / Q000503:physiopathology*; D006736:Horses; D066298:In Vitro Techniques; D050279:Metacarpal Bones / Q000293:injuries* / Q000503:physiopathology*; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013314:Stress, Mechanical