Some 30 years ago, we applied the newly described method of dual photon absorptiometry (DPA) to demonstrate that osteoporotic women with vertebral fractures had lost substantially more bone from the vertebrae than controls. This opened a whole new field of research into the determinants of bone loss and fractures in the axial skeleton and set the stage for subsequent development of dual-energy x-ray absorptiometry (DXA) and quantitative computed tomography (QCT), which are now the standard methods for assessing osteoporosis severity and treatment efficacy.