Biomechanical testing of fixed and adjustable femoral cortical suspension devices for ACL reconstruction under high loads and extended cyclic loading

Abstract

Purpose: To compare loop elongation after 5000 cycles, loop-elongation at failure, and load at failure of the fixedloop G-Lok device and three adjustable-loop devices (UltraButton, RigidLoop Adjustable and ProCinch RT), during testing over extended cycles under high loading. Methods: Five devices of each type were tested on a custom-built rig fixed to an Instron machine. The testing protocol had four stages: preloading, cyclic preconditioning, incremental cyclic loading and pull-to-failure. Outcome measures were loop elongation after 5000 cycles, loop-elongation at failure, and load at failure. Results: The loop elongation after 5000 cycles for G-Lok was 1.46 ± 0.25 mm, which was comparable to that of RigidLoop (1.51 ± 0.16 mm, p = 1.000) and ProCinch (1.60 ± 0.09 mm, p = 1.000). In comparison, the loop elongation for UltraButton was 2.66 ± 0.28 mm, which was significantly larger than all other devices (p = 0.048). The failure load for all devices ranged between 1455 and 2178 N. G-Lok was significantly stronger than all adjustable-loop devices (p = 0.048). The elongation at failure was largest for UltraButton (4.20 ± 0.33 mm), which was significantly greater than G-Lok (3.17 ± 0.33 mm, p = 0.048), RigidLoop (2.88 ± 0.20 mm, p = 0.048) and ProCinch (2.78 ± 0.08 mm, p = 0.048). There was no significant difference in elongation at failure for the rest of the devices. Conclusions: Our study has shown that the G-Lok fixed-loop device and the three adjustable-loop devices (UltraButton, RigidLoop Adjustable and ProCinch RT) all elongated less than 3 mm during testing over an extended number of cycles at high loads, nonetheless, the fixed loop device performed best in terms of least elongation and highest load at failure.

In Vitro Testing of 2 Adjustable-Loop Cortical Suspensory Fixation Systems Versus Interference Screw for Anterior Cruciate Ligament Reconstruction

“… 1 In a recent study comparing UB with 2 other ALDs (RigidLoop Adjustable and ProCinch RT), after 5000 cycles, UB showed the largest elongation at failure, although all 3 demonstrated elongations <3 mm over an extended number of cycles at high loads. 36 However, Cheng et al 8 observed that the mechanical properties of the GraftMax ALD were comparable with those of TR.…”

Biomechanical Stability of Third-Generation Adjustable Suture Loop Devices Versus Continuous Loop Button Device for Cortical Fixation of ACL Tendon Grafts

“…Primary stability of ALB button devices has been assessed in a variety of biomechanical studies with different study protocols. 20 , 36 , 41 First, isolated testing of the implant led to lower elongation and higher load to failure in comparison to in vitro ACLR. 6 , 12 , 19 , 24 , 36 However, the influence of the interface between the implant and the cortical bone or the tendon graft is not considered in isolated implant testing.…”

Anatomical rectangular tunnel anterior cruciate ligament reconstruction provides excellent clinical outcomes

“…While an adjustable‐length femoral cortical fixation device can eliminate potential risks associated with the interference screw, such as intra‐articular migration and loss of fixation owing to screw–tunnel divergence, experimental studies have indicated that loop loosening induced by cyclic loads could be a concern [3, 13, 14, 16, 25, 32]. Alternatively, Kusano et al have evaluated CT images obtained 1 and 12 weeks after ART ACL reconstruction with a BTB graft and reported that the loop length change of BTB TightRope ® was negligible in a clinical setting, which was different from an experimental setting [21].…”