Bi- and three-dimensional CT study of carpal bone motion occurring in lateral deviation.

A computed tomography (CT) study of the right wrists of 15 volunteers and of 5 anatomical preparations in neutral position, radial (15 degrees) and ulnar (30 degrees) deviation enables to tackle the qualitative analysis of carpal bone motion. The CT Scans were analyzed and reconstructed in three dimensions by means of the Philips CAMRA S100 computer program. The results show that the capitate, the metacarpals II and III and, to a lesser extent, the trapezium and the trapezoid are poorly mobile. Our study points to the role of the flexor and extensor carpi ulnaris muscles in the stability of the internal carpus, confirming that the pisiform is a sesamoid bone in the flexor carpi ulnaris tendon. A model of longitudinal functional structure of the carpus during lateral deviation, intermediate between those of Navarro and Taleisnik, is proposed.