Dynamic bone quality: a noninvasive measure of bone's biomechanical property in osteoporosis

We describe a novel approach to characterize bone quality noninvasively, a measurement that quantifies aggregate shock-absorption capacity of load-bearing bones as a measure of mechanical structural integrity during exposure to real-time self-induced in vivo loading associated with heel strike. The outcome measure, damping factor, was estimated at 5 load-bearing anatomical sites: ankle, tibial tuberosity, femoral condyle, lower back (at 3rd lumbar vertebra), and upper back (7th thoracic vertebra) plus the forehead in 67 patients with postmenopausal osteoporosis with and without documented vertebral fractures. The damping value was significantly lower in patients with vertebral fractures compared with those without a fracture (range: -36% to -72%; median: -44%). In these women with osteoporosis, damping factor was able to discriminate between patients with and without vertebral fractures, whereas traditional measures of bone density and biomechanical measures obtained from bone geometry were not significantly different between the groups.