Context: Bone mineral density (BMD) is used to diagnose osteoporosis, and often to measure efficacy in osteoporosis treatment trials; however, there is a poor correlation between lumbar spine BMD increases and vertebral fracture risk reduction in patients receiving treatment for osteoporosis.
Objective: The purpose of this article is to review the uses and limitations of BMD measurements and the relationship between BMD and bone strength. DATA SOURCE/STUDY SELECTION: A MEDLINE literature search was conducted with the terms bone mineral density , fracture , osteoporosis , and bone strength as well as the generic names of osteoporosis therapies (alendronate, risedronate, raloxifene, teriparatide, and calcitonin). Search results were limited to English language journals and articles published within the last 20 years. Published abstracts from scientific meetings were also reviewed.
Conclusion: BMD measurement remains the most useful diagnostic tool for identifying patients with osteoporosis. Although they are helpful in guiding decisions to initiate osteoporosis treatment, subsequent changes in BMD provide an imperfect indicator of treatment efficacy. Analyses of clinical trials show an inconsistent relationship between increased spinal BMD and a decreased risk of vertebral fracture. Increased BMD accounts for less than 25% of the overall reduction in fracture risk in most instances. Consequently, fracture risk reduction itself remains the most clinically relevant therapeutic outcome of osteoporosis therapy.