Biomechanical Evaluation of Scaphoid and Lunate Kinematics Following Selective Sectioning of Portions of the Scapholunate Interosseous Ligament

PurposeTo determine the relative roles of the dorsal and volar portions of the scapholunate interosseous ligament (SLIL) in the stability of the scaphoid and lunate.MethodsSixteen fresh cadaver wrists were moved through physiological motions using a wrist joint simulator. Electromagnetic sensors measured the motion of the scaphoid and lunate. Data were collected with the wrist intact, after randomly sectioning the dorsal SLIL first (8 wrists) or the volar SLIL first (8 wrists), and after full ligamentous sectioning. Differences in the percent increase in scaphoid flexion or lunate extension were compared using a t test with significance set at P < .05.ResultsSectioning the dorsal SLIL accounted for 37%, 72%, and 68% of the increase in scaphoid flexion in wrist flexion-extension, radioulnar deviation, and dart throw motion as compared with complete SLIL sectioning. Sectioning the volar SLIL accounted for only 7%, 6%, and 14%, respectively. In the same 3 motions, sectioning the dorsal SLIL accounted for 55%, 57%, and 58% of the increase in lunate extension, whereas volar SLIL sectioning accounted for 27%, 28%, and 22%.ConclusionsThe dorsal SLIL provides more stability to the scaphoid and lunate in biomechanical testing. The volar SLIL does provide some, although less, stability.Clinical relevanceAlthough this study supports the critical importance of dorsal SLIL repairs or reconstructions, it also shows that there may be some value in implementing a volar SLIL repair or reconstruction.