To investigate a new incidence and preventive effect of menatetrenone on vertebral fracture in patients with osteoporosis who were randomly assigned to either treatment arm receiving daily dose of calcium supplement as a monotherapy (calcium monotherapy group) or menatetrenone plus calcium supplement as a combination therapy (menatetrenone combo therapy group) for 36 months, followed by a 12-month follow-up observation to examine the preventive effect on the fracture risk.