Association of Extrinsic Ligament Injury with Diastasis in Scapholunate Ligament Injury.

PURPOSE: Extrinsic ligament injury is necessary for scapholunate (SL) diastasis to occur in SL ligament injury. Prior studies demonstrate an association between dorsal extrinsic ligament injury and SL diastasis, but it is unclear what is the importance of volar extrinsic injury. This study aimed to characterize injury to the dorsal intercarpal ligament (DIC), dorsal radicarpal ligament (DRC), volar extrinsic ligaments (LRL/SRL/RSC), and scaphotrapezotrapezial (STT) ligaments to determine what extrinsic ligament injuries are independently associated with SL diastasis.

METHODS: We conducted a retrospective cohort at a multicenter academic institution and identified 101 patients with magnetic resonance imaging (MRI)-confirmed SL ligament injuries from 2018 to 2023. Three musculoskeletal radiologists independently assessed the MRIs for the presence of SL ligament injuries, volar extrinsic ligament (LRL/SRL/RSC), STT ligament, and dorsal extrinsic ligament (DIC and DRC) injuries and quantified SL diastasis.

RESULTS: In patients with SL diastasis > 2 mm, injuries to the volar extrinsic ligaments (LRL/SRL/RSC) were found in 42% of cases compared to 11% in those without SL diastasis. Dorsal extrinsic injuries (DIC and/or DRC) were more frequently observed in cases with SL diastasis (60%) than in those without SL diastasis (25%). Injury to the volar extrinsic ligaments and any of the dorsal extrinsic ligaments (DIC and/or DRC) was significantly associated with SL diastasis (OR, 4.44; 95% CI, 1.51-14.27 and 3.39, 95% CI, 1.33-8.93, respectively; P < .05). The interobserver agreement showed fair to moderate agreement on injured ligaments and substantial for uninjured extrinsic ligaments.

CONCLUSIONS: This study demonstrates that in patients with MRI-confirmed SL diastasis, injury to either the volar extrinsic ligaments or the dorsal extrinsic ligament injuries are each independently associated with SL diastasis > 2 mm. Volar extrinsic ligament insufficiency alone is meaningful in scapholunate instability and may influence reconstruction strategies based on the specific ligamentous structures involved.

TYPE OF STUDY/LEVEL OF EVIDENCE: Retrospective cohort study IV.