Ulnar translation of the carpus in rheumatoid arthritis: an analysis of five determination methods.

Five x-ray methods of assessing ulnar translation of the carpus were compared to each other. Overall, we found the uncompensated semiquantitative method proposed by Gilula et al. to be the most practical and the best method with a sensitivity index of 82%, a specificity index of 88%, an accuracy of 87%, and an interobserver correlation of 90%. The method, however, decreased in specificity and accuracy when a corrective formula was applied to adjust the ulnometacarpal angle to zero degrees deviation. Our conclusion is that the sensitivity indices are relatively low for all methods, and underdiagnosis may occur. At present the semiquantitated method of Gilula et al. is the most practical, with the highest sensitivity index, and is recommended as a screening tool for assessment of ulnar translation of the carpus.