Radiogrammetry of the metacarpal: a critical reappraisal.

The precise estimation of osteoporosis is hampered by the lack of a generally accepted method of evaluation. Measurement of the combined cortical thickness (CCT) of the centre point of the second metacarpal has been widely used for this purpose, but the wide normal variation found in population studies has reduced its value in the diagnosis of this condition in the individual. The factors leading this normal variability are discussed and the three centre metacarpals are compared with each other. It is concluded that simple CCT measurement is preferable to any of the indices so far devised, but that a single measurement of a given metacarpal is too imprecise to be of real value. If a single metacarpal is to be chosen, three measurements of the third metacarpal gives a coefficient of variation lower than those of the second or fourth, and an average of nine measurements of the three centre metacarpals produces a further useful reduction in variability.