Carpal Instability Patterns Reviewed Based on Cases

Background: The wrist is anatomically and biomechanically complex, resulting in a balance that provides both mobility and stability with dynamic loads. Objective: To review biomechanical concepts and highlight the important anatomical structures that, when disrupted, can result in characteristic patterns of carpal instability. Discussion: A case-based review of 6 scenarios has been presented. Case 1 illustrates how a locked volar distal radioulnar joint (DRUJ) dislocation emphasizes the distal radioulnar ligaments as the primary stabilizer of the DRUJ. There is also increasing evidence that the distal oblique band of the interosseous membrane provides additional stabilization. The pronator quadratus and extensor carpi ulnaris tendon provide dynamic stabilization. In case 2, a distal radial physeal premature closure demonstrates importance of ulnar variance in distribution of axial load at the wrist with cases of positive ulnar variance resulting in ulnar impaction and negative ulnar more...