ABSTRACT
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.
Subject(s)
Cartilage, Articular/injuries , Joint Dislocations/physiopathology , Ulna Fractures/physiopathology , Weight-Bearing/physiology , Wrist Injuries/physiopathology , Adult , Biomechanical Phenomena , Cartilage, Articular/physiopathology , Humans , Male , Models, Anatomic , Rupture , Wrist Joint/physiopathologyABSTRACT
The articular disk of the triangular fibrocartilage complex was studied using a video imaging system in a cadaveric laboratory experiment. Changes in disk configuration consistently occurred during pronation and supination and resulted in a nonuniform strain distribution that was dependent upon forearm position. Strains occurred primarily in the radioulnar axis of the disk, with dorsoanterior strains being negligible. Strains were concentrated in the radial portion of the disk and were highest with the forearm pronated. Application of a distraction load to the distal radioulnar joint to simulate the effect of axial wrist loading caused strains to increase the most in the radial portion. These findings suggest that joint distraction loading and forearm pronation are important components of the injury mechanism for the most common type of traumatic tear that occurs near the radial attachment of the disk.
