Internal Bracing Augmentation for Scapholunate Interosseous Ligament Repair: A Cadaveric Biomechanical Study

Purpose: Internal bracing (IB) is an augmentation method using high-strength nonabsorbable tape. This study compared scapholunate interosseous ligament (SLIL) repair alone, SLIL repair with IB augmentation (RIBA), and native intact SLIL (NIS) in a biomechanical cadaveric model. Methods: We used 21 specimens of fresh-frozen wrists in this study (7 matched pairs, SLIL repair-only and SLIL RIBA groups; and 7 independent fresh-frozen wrists, NIS group). In the SLIL RIBA group, augmentation using IB was performed after the repair. The specimens were preloaded and cyclically loaded in tension. Maximum extension and hysteresis were measured in all specimens. The specimens were subsequently tested for load to failure. Failure load (yield point load, mean ultimate load, and load at clinical failure) and linear stiffness were calculated. Results: In cyclic tensile testing, RIBA showed lower maximum extension and lower hysteresis than repair alone. In load to failure testing, the yield point load was statistically higher in the RIBA (59.3 N) group than in the repair-only (30.4 N) group but showed no significant difference compared with the NIS (90.7 N) groups. Moreover, the RIBA (98.5 N) group showed higher and lower mean ultimate loads than the repair-only (37.7 N) and NIS (211.8 N) groups, respectively. Load at clinical failure was higher with RIBA than with repair alone (3-mm extension: 70.0 vs 26.4 N; 4-mm extension: 84.1 vs 33.4 N). Repair alone and RIBA had comparable linear stiffness (38.2 vs 44.1 N/mm). Conclusions: Although SLIL RIBA did not recreate biomechanical properties equivalent to those of NIS, it demonstrated a significantly higher strength than repair alone. Clinical relevance: Repair with IB augmentation could serve as a novel surgical technique that enhances SLIL direct repair through biomechanical support.