These results indicate that ZOL treatment inhibited bone loss and trabecular selleck products deterioration that has previously been shown to occur after ovariectomy [13]. Table 1 Cortical thickness, trabecular bone volume, and
trabecular microarchitecture as determined by micro-CT in L4 vertebrae (mean ± SD) from SHAM-OVX and OVX-ZOL rats BV/TV (−) Conn.D (1/mm3) SMI (−) Tb.N (1/mm) Tb.Th (μm) Tb.Sp (μm) Cortical thickness (μm) SHAM-OVX (n = 7) 0.288 (±0.034) 60.5 (±25.0) 0.554 (±0.319) 3.27 (±0.583) 89.4 (±5.3) 290 (±46) 174 (±12) OVX-ZOL (n = 5) 0.285 (±0.043) 43.8 (±11.5) 0.425 (±0.461) 2.91 (±0.500) 95.8 (±1.5) 335 (±70) 183 (±12) Parameters in bold are PX-478 in vivo significantly different between groups (p < 0.05 by unpaired t test) Fatigue compression tests For all failed samples, force–displacement cycles displayed typical fatigue behavior characterized by decreasing secant stiffness, increasing hysteresis, and increasing nonlinearity (Fig. 2). Displacement increased over time due to mostly creep and to a lower extent, decreasing
secant selleck chemicals stiffness. For each sample, the steady-state creep rate was determined from the apparent strain versus time curve, as well as the time to failure and apparent strain at failure (Fig. 3). Time to failure, apparent strain at failure, steady-state creep rate, initial stiffness, and percent loss of stiffness at failure were not significantly different between the two groups (Table 2). Steady-state creep rate and log of the time to failure have shown to be inversely linearly correlated in compressive fatigue very studies on bovine trabecular bone [32, 33]. Here, we also found a strong inverse correlation between log of
the steady-state creep rate and log of the time to failure of all samples taken together (r 2 = 0.86, p < 0.001, Fig. 4). The relationship between steady-state creep rate and time to failure was similar between SHAM-OVX and OVX-ZOL. Fig. 4 Steady-state creep rate plotted against time to failure for all samples on a log–log scale. A significant inverse linear correlation was found between log of the time to failure and log of the steady-state creep rate (r 2 = 0.84, p < 0.001) Table 2 Compressive fatigue properties determined in L4 vertebrae (mean ± SD) from SHAM-OVX and OVX-ZOL rats Time to failure (h) Apparent strain at failure (%) Steady-state creep rate (%/h) Initial stiffness (N/mm) Loss of stiffness (%) SHAM-OVX (n = 7) 5.42 (±4.67) 4.19 (±1.52) 0.80 (±1.25) 2,193 (±285) 20.11 (±6.68) OVX-ZOL (n = 5) 5.51 (±5.80) 4.30 (±1.50) 0.50 (±0.37) 2,396 (±191) 16.96 (±9.59) Relation between morphology and fatigue properties BV/TV, Conn.D, Tb.N, and Tb.Sp each correlated with apparent strain at failure as well as with log of the apparent strain at failure (0.31 < r 2 < 0.50, p < 0.05). All other correlations between morphologic parameters and fatigue properties were not significant (Fig. 5). Fig.