PITFALLS IN THE MEASUREMENT OF BONE-MINERAL DENSITY BY DUAL-ENERGY X-RAY ABSORPTIOMETRY

Study Design. Fifty-three human thoracic and lumbar vertebrae were ana lyzed by dual energy x-ray absorptiomety to obtain projectional (g/cm( 2)) and volumetric (g/cm(3)) bone mineral density. Objectives. To dete rmine the effect of volume on the measurement of bone mineral density by DEXA. Summary of Background Data. Despite the widespread use of dua l energy x-ray absorptiomety to measure bone mineral density expressed as grams per projectional unit area (g/cm(2)), the effect of volume h as been ignored in many published biomechanical studies. Methods. Proj ectional bone mineral density (g/cm(2)) of fifty-three human vertebrae was obtained by dual energy x-ray absorptiomety measurement. This as compared to bone mineral density expressed as grams per unit volume. R esults. Many specimens with near equal projectional bone mineral densi ty were demonstrated to have significantly different true densities wh en measured by dual energy x-ray absorptiomety in grams per unit volum e. The difference in true bone mineral density for these specimens ran ged from 24.1% to 139%. Conclusion. The effect of volume on bone miner al density data based on projectional areas can cause very significant perturbations of the data in biomechanical studies.