RESUMO
BACKGROUND: Surgical treatment of Rockwood grade V AC joint injuries remains varied. We hypothesized that the addition of a second suspensory device between the clavicle and coracoid would yield superior biomechanical results over a single device. We also hypothesized that the addition of an internal brace across the AC joint to a suspensory device would yield superior results over the suspensory device in isolation. METHODS: A total of 24 cadaveric shoulders were dissected and randomized to four groups with four different constructs implanted: Group A: Single AC TightRope (Arthrex Inc., Naples, FL, USA) Group B: Double AC TightRope Group C: Single Knotless AC TightRope (Arthrex Inc., Naples, FL, USA) Group D: Single Knotless AC TightRope with AC InternalBrace Ligament Augmentation (Arthrex Inc., Naples, FL, USA) These were then loaded in the Robotic arm (SIMVITRO) where 250 cycles of 50N of force in the superior plane was applied. Dynamic creep, displacement, translation and stiffness were assessed. RESULTS: Testing was successfully completed for all specimens. There were no failures due to fracture or translation of the clavicle greater than 5mm from the starting position. Reduction was maintained with a mean superior displacement of 1.7 mm (± 1.4 mm). The mean peak to peak displacement, superior and posterior translation, dynamic creep and stiffness did not differ significantly between construct groups. CONCLUSION: This study did not demonstrate any significant biomechanical differences between groups in terms of displacement, translation, creep or stiffness.