What is the Most Critical Secondary Stabilizer for Preventing Scapholunate Dissociation? Cadaveric Biomechanical Evaluation

Introduction

Isolated injury of the scapholunate interosseous ligament (SLIL) is insufficient to produce dorsal intercalated segment instability. Static instability of the scapholunate joint may occur when the damage to the secondary stabilizers is accompanied. There is no consensus on which secondary stabilizers are most important in preventing scapholunate dissociation, but many authors have reported the importance of dorsal intercarpal (DIC), scaphotrapeziotrapezoid (STT), and long radiolunate (LRL) ligament. The purpose of this study was to evaluate the role of the DIC, STT, and LRL ligaments in preventing scapholunate dissociation.

Methods

Thirty fresh-frozen upper extremity cadaveric specimens were prepared. A wrist simulator with a linear guide rail system (tendon load/motion-controlled system) and a motion capture system were used. The scapholunate (SL) distance, radioscaphoid angle (RSA), radiolunate angle (RLA), and scapholunate angle (SLA) were measured through continuous flexion-extension and ulnar deviation–radial deviation movements. Results were compared in five conditions: (1) intact, (2) SLIL section, (3) DIC section, (4) STT section, and (5) LRL section. Sections of the DIC, STT, and LRL ligaments were assigned in random order.

Results

Sectioning of the only SLIL was not sufficient to alter the normal kinematics of the SL joint. The SLIL+DIC section had the greatest effect on SL distance widening. According to RSA, the SLIL+STT section had a greater effect on scaphoid flexion deformity, but the difference was not significant. According to RLA, the SLIL+LRL section had a greater effect on the lunate extension deformity, but the difference was also not significant. In terms of SLA, the SLIL+DIC section had the greatest effect on SL rotation.

Conclusions

• Among many secondary stabilizers, the DIC ligament had the greatest impact on the distraction and rotational strength of the SL joint.
• Techniques to reconstruct DIC should be considered when treating SL dissociation.