Dynamic changes in the shape of the triangular fibrocartilage complex during rotation demonstrated with high resolution magnetic resonance imaging.

We studied in vivo dynamic changes in the triangular fibrocartilage complex (TFCC) in ten healthy volunteers using high-resolution magnetic resonance imaging (MRI). A custom made surface coil, which was specially designed to allow movements of the wrist in all directions, was used in this study. MR images in the axial and coronal planes were acquired at maximum pronation, in the neutral position and at maximum supination. During pronation and supination, little deformity of the disc proper was seen on axial sections. In contrast, the ulnar side of the TFCC around the ulnar styloid process showed obvious dynamic changes. The ulnar head translated palmarly to the radius in supination and dorsally in pronation, while there was little change in the position of the fovea of the ulna in relation to the radius. Considering the three-dimensional structure of the TFCC, these findings suggest that the disc proper is strong enough to support the ulnar carpus with little deformity during rotation and that the triangular ligament twists at its origin. During rotation there is friction between the proximal side of the disc proper and the ulnar head. On coronal sections, the disc proper became thinner in pronation due to increased ulnar variance.