PREDICTION OF VERTEBRAL AND FEMORAL STRENGTH IN-VITRO BY BONE-MINERALDENSITY MEASURED AT DIFFERENT SKELETAL SITES

The aim of the present study was to investigate the prediction of vert ebral and femoral strength in vitro by bone mineral density (BMD) meas ured at different skeletal sites. The third lumbar vertebral body, the right proximal femur, and the right calcaneus were removed from 38 ma le and 32 female cadavers (mean age 69 years, range 23-92 years). Area l BMD of all bone specimens was determined by dual-energy X-ray absorp tiometry (DXA). The failure load of the vertebral body and the femur w as determined by mechanical testing. Vertebral and femoral strength we re both greater in males than females (p < 0.01), as was BMD at all si tes (p < 0.01). Vertebral strength correlated well with vertebral BMD (r(2) = 0.64) but was only moderately correlated with BMD measured at the femur (r(2) = 0.36) or the calcaneus (r(2) = 0.18). Femoral streng th showed the highest correlations with femoral BMD (r(2) = 0.88) and somewhat weaker relationships with BMD at the vertebra (r(2) = 0.50) a nd the calcaneus (r(2) = 0.54). BMD values at the vertebra, femur, and calcaneus were only moderately interrelated (r(2) = 0.31-0.65), and v ertebral strength correlated only modestly with the strength of the fe mur (r(2) = 0.36). These in vitro results support the concept that opt imal prediction of vertebral or femoral strength by DXA requires site- specific assessments.