Randomized, Open, Parallel, Active Controlled Study on Fracture Prevention in Antiosteoporosis Treatment (OF Study)

Inclusion criteria

Inpatient or outpatient is not asked. If using any anti-osteoporotic agent other than calcium preparations (i.e., contraindicated for concomitant use stipulated in the protocol of this post-marketing study), such agent must be discontinued. Even after the discontinuation, calcium dosing is permitted with a condition that the subsequent use is started after a 8-week elapse from the discontinuation. * Patients with primary osteoporosis (diagnosed according to Diagnostic Criteria for Primary Osteoporosis issued by the Japanese Society for Bone and Mineral Research (1995). * Post-menopausal patients aged 50 years or older. * Patients who agree to participate in a 4-year follow-up observation. * Patients who provide written informed consent. Exclusion Criteira: * Patients on warfarin potassium (Warfarin®) therapy. * Patients with hypercalcemia. * Patietns with renal calculus. * Patients with a known history of hypersensitivity to calcium or menatetrenone preparations. * Patients with severe complication in the hepatic, renal, gastrointestinal, cardio- and cerebrovascular system. * Patients who underwent bilateral ovariectomy. * Patients with radiotherapy in the pelvis or para-aortic area. * Patients with the following X-ray findings; 1. Patients showing osteophytes connecting with adjacent vertebral osteophytes 2. Patients showing hyperostosis of ligament around the vertebral body 3. Patients showing inter-body fusion 4. Patients who experienced surgical intervention(s) in the spine 5. Patients with scoliosis which disturbs a diagnosing of vertebral fracture * Patients who have been treated with anti-osteoporotic agents, other than calcium preparation, within 8 months prior to the study treatment (but not applied to the following; if discontinued, non-treated, or shifted to calcium monotherapy for 8 weeks or longer before starting the study treatment). * Patients who experienced bisphosphonates in the past. * Patients who are likely to show insufficient absorption of liposoluble agents such as biliary atresia, impaired bile secretion, etc. * Other patients who are judged to be ineligible for study entry by the investigator or investigator.