What is the most critical secondary stabilizer in preventing scapholunate dissociation?

Aims Isolated injury of the scapholunate interosseous ligament (SLIL) will not produce static instability of the scapholunate joint. For this, secondary stabilizers must also be compromised. There is no consensus on which secondary stabilizer is the most important in preventing static scapholunate instability (SLI), but many studies have reported the importance of dorsal intercarpal (DIC), scaphotrapeziotrapezoid (STT), and long radiolunate (LRL) ligaments. The purpose of this study was to evaluate the roles of the SLIL, DIC, STT, and LRL ligaments in preventing scapholunate dissociation. Methods A total of 36 fresh-frozen upper limb cadaveric specimens were prepared. A wrist motion simulator with a linear guide rail system (tendon load/motion-controlled system) and five motion capture systems were used. The experimental groups were as follows: 1) intact wrist and ligaments, 2) SLIL transection, 3) DIC transection, 4) STT transection, and 5) LRL transection. The DIC, STT, and LRL ligament transections were randomly assigned. The scapholunate distance, radioscaphoid angle (RSA), radiolunate angle (RLA), and scapholunate angle (SLA) were measured during continuous extension-flexion and ulnar deviation–radial deviation movements. Results Isolated transection of the SLIL was not sufficient to alter the normal kinematics of the SL joint. However, when the DIC ligament was transected in the first stages, a significant increase in the scapholunate distance was observed, and significant changes were observed in the RSA and SLA. Furthermore, when the DIC was transected in the second and third stages, the increase in scapholunate distance was significantly greater than that with transection of the other ligaments. Conclusion The DIC ligament demonstrated the greatest influence on both distraction and rotational stability of the scapholunate joint. Cite this article: Bone Joint Res 2026;15(11):1341–1349.