Atraumatic or noninvasive methods for assessing the status of bone can be divided into two major groups; radiologic and nonradiologic. The former use ionizing radiation, including radiation produced by X-ray tubes, radioactive isotopes, and accelerators, namely photons and neutrons. Nonradiologic methods, such as ultrasound (Jurist, 1970; Langeton et al, 1984) and measurement of skinfold thickness (Brincat et al, 1984), are still in a developmental stage for application to bone, and therefore will not be discussed further.

The radiologic methods comprise three major subgroups: qualitative, semiquantitative, and quantitative methods. Qualitative methods depend largely on the more or less subjective interpretation of radiographs. Semiquantitative analysis of radiographs uses a defined system for grading qualitative features -- eg, the Singh index of the proximal end of the femur (Singh et al, 1970) and the index of striation of the metacarpi (Meema and Schatz, 1970). By far, most methods are quantitative, the subject of this review.