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 se en on axial sections. In contrast, the ulnar side of the TFCC around the ul nar styloid process shoved obvious dynamic changes. The ulnar head translat ed palmarly to the radius in supination and dorsally in pronation, while th ere 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, the se findings suggest that the disc proper is strong enough to support the ul nar carpus with little deformity during rotation and that the triangular li gament twists at its origin. During rotation there is friction between the proximal side of the disc proper and the ulnar head. On coronal sections, t he disc proper became thinner in pronation due to increased ulnar variance.