Impact of Oral Ibandronate 150 mg Monthly on Structural Properties of Bone in Postmenopausal Osteoporosis (SPIMOS-3D)

Inclusion Criteria: * Age between 60 and 75 years * Menopause \> 5 years * Spine (L1 - L4) or hip BMD ≤ -2.0 and \> -3.5 SD T-score measured by DXA * Patients who, in the opinion of the investigator, are able and willing to comply with the protocol for its duration * Written informed consent * 3DpQCT measurable at both skeletal sites, distal tibia and radius Exclusion Criteria: * Spine or hip BMD ≤ -3,5 SD T-Score measured by DXA * Vertebral fractures * Multiple (\>2) low trauma peripheral fractures * Disease/disorder known to influence bone metabolism * History of major upper gastro-intestinal (GI) disease * Diagnosed malignant disease within the previous 10 years * Previous treatment with a bisphoshonate at any time * Treatment with fluoride for osteoporosis (dose greater than 10 mg/day) within the last 12 months, or for more than 2 years (total duration) * Treatment with PTH and similar agents or strontium ranelate at any time * Treatment with other drugs affecting bone metabolism within the last 6 months * Chronic systemic corticosteroid treatment * Estrogens, progestins, SERMs, anabolic steroids, active vitamin D analogues/metabolites, calcitonin * Calcineurin inhibitors (e.g. cyclosporine, tacrolimus) or methotrexate * Total serum calcium \< 2.2 mmol/l or \> 2.6 mmol/l * Vitamin D deficiency (serum 25-hydroxy vitamin D \< 12 ng/ ml) * ALT above triple upper limit of normal range * Renal impairment (serum creatinine \> 210 µmol/l) * Contra-indications for ibandronate, calcium or vitamin D * Employees of the Centre for Muscle and Bone Research, or their relatives