Biomechanical Comparison of Adjustable-Loop Femoral Cortical Suspension Devices for Soft Tissue ACL Reconstruction

Abstract

Several new adjustable-loop devices (ALDs) for anterior cruciate ligament reconstruction (ACLR) have not been tested in vitro. To compare the biomechanical performances of 5 ALDs under a high cyclic load and forces representative of the return-to-play conditions seen in the recovering athlete. Controlled laboratory study. A total of 10 devices for each of 5 chosen ALDs (UltraButton [Smith & Nephew], RigidLoop [DePuy Mitek], ProCinch [Stryker], TightRope [Arthrex], and ToggleLoc [Biomet]) were tested in a device-only model. The devices were secured to a servohydraulic test machine and preconditioned from 10 to 75 N at a rate of 0.5 Hz for 20 cycles. They were then subjected to high cyclic forces (100-500 N for 4000 cycles) and subsequently pulled to failure at 50 mm/min. The preconditioning displacement, permanent deformation, cumulative peak displacement, stiffness coefficient, and load to failure data were collected. The UltraButton displayed the greatest preconditioning displacement (0.22 ± 0.20 mm), followed by the RigidLoop (0.11 ± 0.03 mm), ProCinch (0.07 ± 0.04 mm), TightRope (0.07 ± 0.02 mm), and ToggleLoc (0.02 ± 0.03 mm). The TightRope displayed the greatest permanent deformation (3.19 ± 1.03 mm) followed by the UltraButton (2.14 ± 0.92 mm), ToggleLoc (2.02 ± 1.09 mm), RigidLoop (1.67 ± 0.1 mm), and ProCinch (1.38 ± 0.18 mm). The TightRope displayed the greatest cumulative peak displacement (3.69 ± 1.03 mm) followed by the UltraButton (2.46 ± 0.92 mm), ToggleLoc (2.37 ± 1.08 mm), RigidLoop (2.01 ± 0.1 mm), and ProCinch (1.75 ± 0.19 mm). The UltraButton displayed the largest stiffness coefficient (1347.22 ± 136.33 N/mm) followed by the RigidLoop (1325.4 ± 116.37 N/mm), ToggleLoc (1216.62 ± 131.32 N/mm), ProCinch (1155.56 ± 88.04), and TightRope (848.48 ± 31.94). The ToggleLoc displayed the largest load to failure (1874.42 ± 101.08 N) followed by the RigidLoop (1614.12 ± 129.11 N), UltraButton (1391.69 ± 142.04 N), ProCinch (1384.85 ± 58.62 N), and TightRope (991.8 ± 51.1 N.). The 5 ALDs exhibited different biomechanical properties. None of them had peak cumulative displacements for which the confidence interval lay above 3 mm, thus no single device was determined to have a higher rate of clinical failure compared with the others. ALD choice may affect biomechanics after ACLR.