Postero-anterior radiography of the wrist. Normal database of carpal measurements.

This study aims to establish a normal database of carpal postero-anterior radiographic measurements that might be a useful alternative to lateral film measurements in clinical practice. Selected landmarks were digitised on 80 postero-anterior wrist radiographs of asymptomatic volunteers. Carpal bone dimensions, ulnar variance, carpal height ratios, radial slope and various carpal angles were computed. Moreover, we describe two new parameters, the scapho-lunate ratios, that may prove useful in the diagnosis of carpal instability. Average values for carpal height, length of metacarpal III, capitate length, ulnar variance, radial slope and classical and revised carpal height ratios agreed with previous findings. Scaphoid length averaged 22 +/- 3 mm, lunate anterior and posterior horn lengths 11 +/- 1 mm and 16 +/- 2 mm respectively. Except for carpal height and length of metacarpal III, standard deviations did not exceed 3 mm. Some of the variation coefficients reached 30% of the average dimension, so that variations, compared to means were not negligible. The standard deviations of angular measurements ranged from 3 degrees to 13 degrees. Further investigations are needed to confirm the usefulness of scapho-lunate ratios.