Effect of triangular ligament tears on distal radioulnar joint instability and evaluation of three clinical tests: a biomechanical study.

Using 11 fresh/frozen cadaver specimens, instability of the distal radioulnar joint (DRUJ) during passive wrist motion was measured by motion analysis and three clinical tests (ulno-carpal stress test, piano-key test, and DRUJ ballottement test) were performed. Release of the triangular ligament from the palmar approach was performed to simulate instability of the DRUJ. Displacement of the distal radius against the ulnar head was measured at various degrees of forearm rotation. Release of the triangular ligament at the ulnar fovea and around the base of the ulnar styloid process caused various degrees of DRUJ instability during passive wrist motion. After complete triangular ligament release, only the DRUJ ballottement test demonstrated a statistically significant degree of accuracy in the evaluation of distal radioulnar joint instability.