title: Bone fragility beyond strength and mineral density: Raman spectroscopy predicts femoral fracture toughness in a murine model of rheumatoid arthritis.
abstract: Clinical prediction of bone fracture risk primarily relies on measures of bone mineral density (BMD). BMD is strongly correlated with bone strength, but strength is independent of fracture toughness, which refers to the bone's resistance to crack initiation and propagation. In that sense, fracture toughness is more relevant to assessing fragility-related fracture risk, independent of trauma. We hypothesized that bone biochemistry, determined by Raman spectroscopy, predicts bone fracture toughness better than BMD. This hypothesis was tested in tumor necrosis factor-transgenic mice (TNF-tg), which develop inflammatory-erosive arthritis and osteoporosis. The left femurs of TNF-tg and wild type (WT) littermates were measured with Raman spectroscopy and micro-computed tomography. Fracture toughness was assessed by cutting a sharp notch into the anterior surface of the femoral mid-diaphysis and propagating the crack under 3 point bending. Femoral fracture toughness of TNF-tg mice was significantly reduced compared to WT controls (p=0.04). A Raman spectrum-based prediction model of fracture toughness was generated by partial least squares regression (PLSR). Raman spectrum PLSR analysis produced strong predictions of fracture toughness, while BMD was not significantly correlated and produced very weak predictions. Raman spectral components associated with mineralization quality and bone collagen were strongly leveraged in predicting fracture toughness, reiterating the limitations of mineralization density alone.
authors.affiliation: Department of Biomedical Engineering, 207 Robert B. Goergen Hall, University of Rochester, Rochester, NY, United States.
authors.forename: Jason A
authors.initials: JA
authors.lastname: Inzana
authors.forename: Jason R
authors.initials: JR
authors.lastname: Maher
authors.forename: Masahiko
authors.initials: M
authors.lastname: Takahata
authors.forename: Edward M
authors.initials: EM
authors.lastname: Schwarz
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Berger
authors.forename: Hani A
authors.initials: HA
authors.lastname: Awad
mesh_terms: D000818:Animals; D001172:Arthritis, Rheumatoid / Q000150:complications / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D015519:Bone Density; D004195:Disease Models, Animal; D005264:Femoral Fractures / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology*; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010024:Osteoporosis / Q000209:etiology / Q000503:physiopathology; D012307:Risk Factors; D013059:Spectrum Analysis, Raman / Q000379:methods*; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000502:physiology; D055114:X-Ray Microtomography
chemical_list: D014409:Tumor Necrosis Factor-alpha