Biomechanical evaluation of the ligamentous stabilizers of the scaphoid and lunate: Part II

PURPOSE: This study is a continuation of our previous investigation of the ligaments stabilizing the scaphoid and lunate. We evaluated the effects of sectioning the scapholunate interosseous ligament, radioscaphocapitate ligament, and scaphotrapezial ligament in 3 sequences. METHODS: Three sets of 8 cadaver forearms were placed in a wrist simulator and moved in continuous cycles of flexion-extension and radial-ulnar deviation. Kinematic data for the scaphoid and lunate were recorded for each wrist in the intact state, after the 3 ligaments were sectioned in various sequences and after the wrist was moved through 1,000 cycles of motion. RESULTS: Sectioning only the scaphotrapezium ligament (ST) or the radioscaphocapitate ligament (RSC) resulted in minimal angular changes to the motion of the scaphoid and lunate. Sectioning of the scapholunate interosseous ligament (SLIL) or 1,000 cycles of repetitive wrist motion after ligament sectioning altered scaphoid and lunate kinematics. CONCLUSIONS: Based on these findings it was concluded that the SLIL is the primary stabilizer and the RSC and ST are secondary stabilizers of the scapholunate articulation. Repetitive motion after ligament injury probably results in further carpal instability.