Sato K, Yamada Y, Kogawa M, et al. - Researchers have adopted a cutoff value of 1.0 mm for vertebral mobility (V-mobility), which is defined as the difference in anterior vertebral height (Ha) between lateral radiographs taken in weight-bearing and non-weight-bearing positions, for determining bone union. In this study, the utility of V-mobility was examined for determining bone union and predicting bone union at 6 months after osteoporotic vertebral fracture (OVFs) onset. Fifty four acute OVFs from T11 to L3 in 53 patients (12 males, 41 females; mean age 82 years; age range 55–97 years) who were hospitalized at ≤ 3 weeks after OVF onset were included in this study. In accordance with Ha on lateral radiographs taken in the sitting position (SIT), lateral decubitus position (DEC), and supine position (SUP), evaluation of vertebral deformity (V-deformity) and V-mobility was done. They defined OVFs indicating V-mobility of ≤ 1.0 mm between SIT and DEC radiographs and no intravertebral cleft on DEC radiograph as semi-union, while those indicating V-mobility of ≤ 1.0 mm between SIT and SUP radiographs and no intravertebral cleft on SUP radiograph as bone union. Per receiver-operating characteristic curve analyses, V-mobility of ≤ 2.1 mm in Ha between SIT and DEC radiographs at 5 weeks after OVF may be a promising indicator for obtaining bone union including semi-union at 6 months after OVF. Findings thereby support the predictive value of V-mobility in the early stage after OVF for bone union at 6 months after OVF and its utility as a quantitative indicator for determining bone union.