The semi-quantitative evaluation of both the absolute values of the apposition bands and the width of daily bone apposition values increased for treated compared to untreated rats, but these effects were not significant. Table 2 Results of the intravital fluorochrome labeling   SHAM SHAM Vib. OVX OVX Vib. OVX vs. SHAM Vib vs. non vib Mean STD Mean STD Mean STD Mean STD p value p value Absolute apposition bandwidth (m -6 ) Calcein green (d0 − d18) 696 275 822 226 1093 182

1032 290 <0.0001 0.4829 Alizarin red (d18–d24) 823 271 804 229 889 181 944 274 0.0267 0.6943 Tetracycline (d24–d35) 659 333 641 226 669 219 709 242 0.4267 0.8278 Sum 2,178 2,267 2,651 2,685             Absolute apposition bandwidth per day (m –6 ) Calcein green (d0–d18) 38.6 15.3 45.7 Selleck GSK3326595 12.5 60.7 10.1 57.3 16.1 <0.0001 0.4877 Alizarin VX-809 nmr Red (d18–d24) 137.2 45.2 134.1 38.2 148.2 30.2 157.3 45.6 0.0269 0.7024 Tetracycline (d24–d35) 59.9 30.3 58.3 20.5 60.8 19.9 64.5 22.0 0.4275 0.8227 Sum 235.7 238.1 269.7 279.1             Relative apposition bandwidth per day (%) Calcein green (d0–d18) 16.8 4.0 19.4 3.4 22.9 3.9 20.7 2.7 <0.0001 0.7371 Alizarin red (d18–d24) 58.5

5.0 56.3 4.7 54.9 3.3 56.2 6.1 0.0436 0.6052 Tetracycline (d24–d35) 24.7 7.0 24.3 4.8 22.2 4.0 23.2 5.5 0.0831 0.8085 The p value of the difference between treated and untreated animals was calculated using a two-way ANOVA. p values <0.05 were considered significant Flat-panel volumetric computed tomography The SHAM group had

a significantly improved BMD, cancellous and cortical bone density compared to OVX animals (p < 0.0001 for all). Vibration led to an improvement of total BMD, cancellous and cortical BMD (Table 1). The cortical bone density after vibration was significantly improved (p = 0.0035), while the BMD (p = 0.0532) and cancellous bone density (p = 0.0634) showed improvement; however, the improvement failed 5-Fluoracil chemical structure to reach significant values. The main disadvantage of the fpVCT used in this study was the lower spatial resolution compared to the µCT. The former method does not allow a detailed description of the trabecular microstructure. Ashing The ash-BMD of SHAM rats was significantly improved compared to OVX rats (p < 0.0001). Vibration yielded a significant improvement of ash-BMD in all groups (p = 0.0011). There were no differences between groups before ashing. After ashing, the SHAM-operated animals had higher ash weights compared to OVX, but these changes were not significant. After calculating the ash-BMD, more differences between the groups were observed (Table 1). Discussion Osteoporosis primarily affects trabecular bone. In humans, the majority of osteoporotic fractures occur in the spine and metaphysis of long bones. In the rat osteopenia model, osteoporosis mainly affects the metaphyseal tibia and lumbar spine [19–23].