Heterogeneity of the mechanical properties of demineralized bone

Knowledge of the mechanical properties of the collagenous component of bone is required for composite modeling of bone tissue and for understanding th e age- and disease-related reductions in the ductility and strength of bone . The overall goal of this study was to investigate the heterogeneity of th e mechanical properties of demineralized bone which remains unexplained and may be due to differences in the collagen structure or organization or in experimental protocols. Uniaxial tension tests were conducted to measure th e elastic and failure properties of demineralized human femoral (n = 10) an d tibial (n = 13) and bovine humeral (n = 8) and tibial (n = 8) cortical bo ne. Elastic modulus differed between groups (p = 0.02), varying from 275 +/ - 94 MPa (mean +/- SD) to 450 +/- 50 MPa. Similarly, ultimate stress varied across groups from 15 +/- 4.2 to 26 +/- 4.7 MPa (p = 0.03). No significant differences in strain-to-failure were observed between any groups in this study (pooled mean of 8.4 +/- 1.6%; p = 0.42). However, Bowman et al. (1996 ) reported an average ultimate strain of 12.3 +/- 0.5% for demineralized bo vine humeral bone, nearly 40% higher than our value. Taken together, it fol lows that all the monotonic mechanical properties of demineralized bone can display substantial heterogeneity. Future studies directed at explaining s uch differences may therefore provide insight into aging and disease of bon e tissue. (C) 1999 Elsevier Science Ltd. All rights reserved.