An alternative method for determination of the carpal height ratio.

Radiographs of the wrist often do not include the entire third metacarpal, so the standard method for measurement of the carpal height ratio (the carpal height divided by the length of the third metacarpal) cannot be used. In this study, the ratio of the carpal height relative to the length of the capitate was evaluated for its suitability as a reproducible alternative. The revised carpal height ratio (the carpal height divided by the capitate length) was evaluated for reproducibility and clinical utility in both in vitro and in vivo studies: it was determined from the radiographs of ten cadaveric wrists; those of 100 wrists (fifty pairs) of normal volunteers, made with controlled positioning; those of 100 wrists, drawn at random from radiographs that had been previously interpreted as showing normal findings; and those of fifty wrists of twenty-nine patients who had documented rheumatoid arthritis. The new ratio was found to be constant in the normal population, consistent bilaterally, decreased in patients who had carpal collapse, and reproducible.