Stability of the distal radioulnar joint contributed by the joint capsule

The distal radioulnar joint (DRUJ) capsule is assumed to be an important stabilizer of the DRUJ. There are few published data regarding the capsule and its specific contribution to stability of the DRUJ. We analyzed the contribution of the joint capsule to DRUJ stability in a biomechanical study consisting of collection of force/displacement data from 16 adult human cadaveric upper extremities. Each specimen was subjected to anteroposterior translation testing of the radius relative to the ulna in 3 positions of forearm rotation (neutral, 60° pronation, 60° supination) by serial sectioning of the DRUJ capsule. The experimental conditions tested included intact capsule, sectioned dorsal capsule, sectioned volar capsule, and repaired capsule. Isolated dorsal capsule sectioning resulted in volar instability of the radius to the ulna primarily in the maximum pronated position. Significant dorsal instability of the radius was observed after isolated volar capsule sectioning in the maximum supinated position. The restabilizing effect of capsule shortening was observed near the maximums of forearm rotation. The additional stability owing to capsule shortening surpassed that of the distal radioulnar ligament at these positions. We showed the effect of capsular injury on DRUJ joint stability and the restabilizing effect of capsule shortening. The importance of the capsule to DRUJ stability should be considered when planning surgical procedures to restore the unstable DRUJ.