Stabilization of the scapholunate interval with interference fit screws: How to do it safely

Scapholunate instability is a common wrist injury that significantly affects wrist function and biomechanics. This study compares three internal brace fixation methods for stabilizing the scapholunate interval in cadaveric models with a control group with intact ligaments (Group C): (1) internal brace without interference screw (Group N), (2) internal brace outside the interference screw (Group O), and (3) internal brace within the interference screw (Group I). The study aims to evaluate biomechanical stability, bone integrity, and osteolysis risk. Thirty-two cadaveric wrists were divided into four groups and subjected to biomechanical testing, including static, dynamic, and failure tests. Results showed that Group C exhibited a maximum failure load at 347.6 ± 21.4N; Group I exhibited the highest maximum failure load (319.4 N ± 28.7 N) and no recurrence of Dorsal Intercalated Segment Instability (DISI) during dynamic testing. Group N demonstrated the lowest biomechanical strength (118.5 N ± 15.3 N) and a 75 % DISI recurrence rate. Group O showed intermediate performance, with a maximum failure load of 221.7 N (±24.6 N) and a 37.5 % DISI recurrence rate. Imaging evaluation revealed that Group I had the least bone damage (2.1 % ± 0.9 %), while Group N had the most (24.8 % ± 2.3 %). The study concludes that placing the internal brace within the interference screw (Group I) offers superior biomechanical stability and bone protection, making it a promising technique for scapholunate stabilization. However, further clinical studies are needed to confirm these findings.