Bone Quality and THA surgical technique Osteoporosis (brittle bones) is defined as a chronic systemic skeletal disease characterized by low bone mineral density (osteopenia) and microarchitecture changes in the trabecular bone structure resulting in reduced strength and therefore increased risk of fractures. Among Danish women over 65 years of age, the prevalence of osteoporosis is 40-60%, and the prevalence among men is increasing. Much effort is put into secondary fracture prophylaxis such as vitamin D and calcium as well as medical bone anti-resorptive treatment (i.e. bisphosphonates).