Triangular fibrocartilage injury: a laboratory model.

A potential injury mechanism for triangular fibrocartilage tears and ulnar styloid fractures was investigated in cadaver specimens. The distal radioulnar joint was distracted to failure, thus applying a tensile force to the triangular fibrocartilage. During distraction, strains in the triangular fibrocartilage and the anatomic site of disruption were recorded with an image analysis system. Complete avulsion of the triangular fibrocartilage from the ulnar head occurred in 7 of 10 specimens. No ulnar styloid fractures occurred. Although strains were high in the radial portion of the disk (28%), no tears occurred in the substance of the disk or at its attachment to the radius. These findings suggest that distal radioulnar joint distraction can cause avulsion of the triangular fibrocartilage. However, ulnar styloid fractures and tears within the disk are more likely caused by injury mechanisms that include shear or compressive forces. Since complete avulsions of the triangular fibrocartilage occurred without a fracture, the absence of a fracture does not rule out a destabilizing injury to the distal radioulnar joint.