The Roles of Bone Mineral Density, Bone Turnover, and Other Properties in Reducing Fracture Risk During Antiresorptive Therapy  Solomon Epstein, MD  Mayo Clinic Proceedings  Volume 80, Issue 3, Pages 379-388 (March 2005) DOI: 10.4065/80.3.379 Copyright © 2005 Mayo Foundation for Medical Education and Research Terms and Conditions

FIGURE 1 Loss of horizontal cross-ties in osteoporotic (OP) bone greatly reduces the strength of the remaining vertical trabeculae (right) compared with normal (N) trabecular bone (left). Increased numbers of resorption pits also create focal areas of weakness, increasing the risk of microfracture (right). Reprinted from Am J Med,6 with permission from Excerpta Medica, Inc. Mayo Clinic Proceedings 2005 80, 379-388DOI: (10.4065/80.3.379) Copyright © 2005 Mayo Foundation for Medical Education and Research Terms and Conditions

FIGURE 2 Distribution of the biochemical marker of bone turnover urinary N-telopeptide (NTx) crosslinks after 2 years of treatment with alendronate (70 mg once a week). The horizontal axis is the randomly assigned patient allocation number. The horizontal dashed lines represent the mean and the lower limit (mean minus 2 SDs) for young, healthy women. BCE = bone collagen equivalents. Data from J Bone Miner Res.7 Mayo Clinic Proceedings 2005 80, 379-388DOI: (10.4065/80.3.379) Copyright © 2005 Mayo Foundation for Medical Education and Research Terms and Conditions

FIGURE 3 Relationship between bone mineral density (BMD) and fracture risk based on a doubling of risk with each SD decrease in BMD (most epidemiological studies have reported relative risks between 1.5 and 2.5 per SD of BMD). A T score of 0 represents the mean BMD for young, healthy women and is assigned a relative risk of 1.0 as the reference value. A relative risk of 2.0 indicates the risk is twice as high compared with the reference value. T scores between −1.0 and −2.5 indicate low bone mass, and values lower than −2.5 indicate osteoporosis. Reprinted from Clin Ther,45 with permission from Excerpta Medica, Inc. Mayo Clinic Proceedings 2005 80, 379-388DOI: (10.4065/80.3.379) Copyright © 2005 Mayo Foundation for Medical Education and Research Terms and Conditions

FIGURE 4 Typical microarchitecture of trabecular bone from a young, healthy person (left) and an older person with osteoporosis (right), illustrating the loss of trabecular connectivity and perforation of trabecular plates. Available at www.osteofound.org/press_centre/visuals.html. Accessed January 19, 2005. Mayo Clinic Proceedings 2005 80, 379-388DOI: (10.4065/80.3.379) Copyright © 2005 Mayo Foundation for Medical Education and Research Terms and Conditions

FIGURE 5 Microcomputed tomographic images of trabecular bone from iliac crest biopsy specimens from participants at the end of a 3-year clinical trial of alendronate (bottom) vs placebo (top). These samples have trabecular volume similar to the means of the alendronate and placebo groups, respectively (trabecular bone volume-total bone volume of 13.9% for the placebo specimen and 19.0% for the alendronate specimen). On average, the alendronate group had significant quantitative improvements in some measures of microarchitecture measured by bone histomorphometry and microcomputed tomography relative to placebo. However, it is difficult to discern this visually; different images of the same sample have strikingly different appearances, depending on the viewing angle. Illustration courtesy of Don Kimmel, PhD, Merck Research Laboratories, West Point, Pa. Mayo Clinic Proceedings 2005 80, 379-388DOI: (10.4065/80.3.379) Copyright © 2005 Mayo Foundation for Medical Education and Research Terms and Conditions