Carpo:metacarpal ratio. A new quantitative measure of radiologic progression of wrist involvement in rheumatioid arthritis.

Analysis of 878 hand films shows the carpo : metacarpal ratio to be a sensitive quantitative index of progression of carpal involvement in rheumatoid arthritis. This index, easily calculated by dividing the lengths of the carpus by the third metacarpal, showed marked consistency in the ratio regardless of age, race, or sex in normal adults. A decreased ratio correlated highly with recognized radiographic stages of rheumatoid arthritis and thus suggested utility in longitudinal studies of patients with this disease.