Madelung's deformity: diagnostic thresholds of radiographic measurements.

PURPOSE: Although the x-ray changes of advanced Madelung's deformity are well described, little quantitative information exists on the subtle, early changes of the deformity. This study investigated the threshold of 4 radiographic measurements that predict a diagnosis of Madelung's deformity by experienced hand surgeons.

METHODS: Ulnar tilt, lunate subsidence, lunate fossa angle, and palmar carpal displacement were measured on x-rays of patients with Madelung's deformity. For each set of x-rays 4 opinions were available concerning a diagnosis of Madelung's deformity as based on the x-rays only. The 4 quantitative measurements were examined to determine a threshold value that predicts a unanimous diagnosis of Madelung's deformity.

RESULTS: The thresholds for the diagnosis of Madelung's deformity are: ulnar tilt of 33 degrees or greater, lunate subsidence of 4 mm or more, lunate fossa angle of 40 degrees or greater, and palmar carpal displacement of 20 mm or more. When any one of these measurements equaled or exceeded this threshold value, the raters were unanimous in establishing a diagnosis of Madelung's deformity.

CONCLUSIONS: Threshold values of ulnar tilt, lunate subsidence, lunate fossa angle, and palmar carpal displacement for the diagnosis of Madelung's deformity are determined. Lunate fossa angle may prove especially useful in the diagnosis of early Madelung's deformity.