Current status of physical measurements of the skeleton.

An overview is presented of some of the major methods of measuring the skeleton in the past 30 years. These include single photon absorptiometry (SPA), dual photon absorptiometry (DPA), quantitative computed tomography (QCT), and recently dual energy radiographic absorptiometry (DRA), also called DEXA (dual energy x-ray absorptiometry). In addition to these methods, all attempting to measure bone mineral density, regional and total body calcium have been determined by in vivo neutron activation analysis (IVNAA). An attempt to determine bone quality as contrasted with bone quantity has been made using ultrasound, with measurements of speed of sound and of attenuation as useful parameters to characterize bone tissue. While the various methods for measuring bone density have been most useful, no one method includes all the features required to be entirely satisfactory: excellent precision and accuracy and the ability to measure volumetric density in gm/cm3. Least successful has been the ability to predict fracture risk, an essential goal in helping the patient.