Primary and secondary stabilizers of the scapholunate joint: a systematic review of cadaveric ligament sectioning studies.

INTRODUCTION: Scapholunate instability is the most common pattern of carpal instability, yet the relative contributions of the intrinsic and extrinsic ligaments remain debated. This systematic review evaluated cadaveric studies of wrist biomechanics assessing kinematic changes following carpal ligament sectioning to clarify the stabilizing roles of individual ligaments.

METHODS: The EMBASE, MEDLINE, Cochrane and Scopus databases were searched from inception to June 2025. Cadaveric studies reporting scapholunate gap (SLG), scapholunate angle (SLA), radiolunate angle (RLA) or dorsal intercalated segment instability (DISI) after ligament sectioning were included. Data were extracted for cumulative and sequential sectioning patterns and synthesized qualitatively.

RESULTS: Thirty-three studies involving 406 wrists were included. With an intact scapholunate interosseous ligament (SLIL), sectioning single or multiple extrinsic carpal ligaments produced minimal changes in SLG, SLA, or RLA. Scapholunate interosseous ligament sectioning increased SLG (mean +1.7 mm), SLA (+8°) and RLA (+3°), with clenched-fist loading further elevating SLG (+0.7 mm) and SLA (+4°). The dorsal intercarpal ligament (DIC) was the dominant secondary stabilizer. Combined SLIL-DIC injury produced the greatest increases across all measures, and DISI occurred only when the SLIL and either the DIC or the scaphotrapeziotrapezoid complex was sectioned.

CONCLUSION: Cadaveric evidence confirms the SLIL as the primary stabilizer of the scapholunate joint and identifies the DIC as the key secondary stabilizer. These biomechanical findings support early diagnosis, targeted reconstruction and the need to restore both primary and secondary stabilizers to prevent progressive scapholunate instability.