Force in the Scapholunate Interosseous Ligament During 2 Simulated Pushup Positions.

PURPOSE: To determine the in vitro force between the scaphoid and the lunate supported by the scapholunate interosseous ligament (SLIL) during 2 wrist pushup positions.

METHODS: Six fresh-frozen cadaveric wrists were tested in a neutral flexion-extension (knuckle) pushup position and in an extended pushup position. Tensile forces were measured across the scapholunate joint as half body weight axial forces were applied through the radius and ulna. Forces were measured after sectioning the SLIL, after also sectioning the dorsal radiocarpal and dorsal intercarpal ligaments, and then after also sectioning the radioscaphocapitate ligament.

RESULTS: In the neutral position with the SLIL sectioned, the tensile force across the scapholunate joint was significantly larger in the extended position (45 N) than in the neutral position (25 N). Sectioning additional ligaments did not significantly increase the measured force. Extrapolation of the measured force in wrist extension with application of 1 time body weight suggests a force of 110 N would occur in the SLIL.

CONCLUSIONS: This study demonstrated that, with the SLIL sectioned, with or without the dorsal radiocarpal, dorsal intercarpal, and radioscaphocapitate ligaments sectioned, the tensile force across the scapholunate joint is greater in extension than in the neutral wrist position.

CLINICAL RELEVANCE: This study helps characterize the forces experienced across the scapholunate articulation when the SLIL is disrupted.