A new radiographic method for evaluation of the position of the carpus in the coronal plane: results in normal subjects

The methods used to quantify pathological variations of the position of the carpus in the coronal plane, mainly ulnar translation of the carpus from t rauma or rheumatoid disease, are often difficult to use in arthritic or pos tsurgical wrists; moreover, they require the measurement of the whole lengt h of the third metacarpal, The aim of this study was to determine a reliabl e and easy-to-use index to analyse the position of the carpus in the corona l plane. One hundred PA X-rays of normal wrists were studied, of which 56 p resented with a medial hamate facet of the lunate. An index of position of the carpus in the coronal plane is defined as the ratio of orthogonal dista nces from [1] the most medial point of the distal radius and [2] the most m edial point of the capitate to the long axis of the radius: its mean value being 1.06 (+/- 0.13) in this series of normal wrists. The index is influen ced by the presence of a medial hamate facet of the lunate, but is not depe ndent on the ulnar head and radial styloid process, nor on the length of th e third metacarpal. To help to define the usefulness of the index in quanti fying the different types of ulnar carpal translations in clinical practice , further studies are required.