The correlation of bone mineral density and biochemical markers to fracture risk

Bone metabolism may be measured indirectly by determining markers for bone formation and bone resorption. Traditionally, total alkaline phosphatase has served to mark bone formation, whereas urine calcium and hydroxyproline, corrected for creatinine, have marked bone resorption. Although these markers have contributed to our understanding of bone metabolism, by themselves they lack the sensitivity and specificity to be helpful in the day-to-day management of patients with osteoporosis. Newer bone markers have been developed and others are currently under development. These markers may be helpful in determining the type of osteoporosis and the response to therapy. Nonetheless, despite their increased sensitivity and specificity, they have not yet been shown to predict future fractures. Many prospective studies have shown that bone mass measured at any site and by any method is inversely related to fracture risk. Site-specific measurement of the bone density of the proximal femur appears to have a stronger relationship to the risk of hip fracture. In predicting spinal fractures, however, measurement of bone density in the lumbar spine does not appear to be substantially superior to measurements of bone density at other sites. The lifetime risk for hip fracture can be estimated from bone mass measurements made in the perimenopausal period. In the future, the combination of baseline perimenopausal bone density and assessments of biochemical markers may better predict future fracture risk; however, this has yet to be shown.