The role of the dorsal scaphotriquetral ligament: a biomechanical study.

INTRODUCTION

The biomechanical role of the dorsal scaphotriquetral ligament (DSTL) ligament in scapholunate (SL) stability remains debated. We assessed DSTL contribution using a cadaveric sectioning model.

METHODS

Twenty-four wrists underwent sequential sectioning: none (phase 0), palmar/proximal scapholunate interosseous ligament (SLIOL) (phase 1), dorsal SLIOL (phase 2), superficial dorsal intercarpal ligament (DICL) (phase 3) and DSTL (phase 4). Under axial loading (60 N; cyclic 60-200 N) and wrist motion, the SL gap and carpal angles, and a CT-derived dorsal instability scaphoid angle (DISA) were measured.

RESULTS

Phase 1 produced no significant instability. Dorsal SLIOL sectioning (phase 2) initiated dynamic instability, with increased SL gap and angles under load and dorsal scaphoid translation, but no resting dorsal intercalated segment instability (DISI). Sectioning the superficial DICL fascicle (phase 3) did not add instability. DSTL sectioning (phase 4) produced the largest changes, with marked SL diastasis, increased angles and DISA, and DISI at rest and under load.

CONCLUSION

Dorsal SLIOL sectioning produced load-dependent (dynamic) SL instability, whereas subsequent DSTL sectioning was associated with progression to static instability, supporting the DSTL as an important dorsal restraint. The DISA may provide an additional CT-based measure of dorsal scaphoid subluxation; however, clinical validation is required.