Previous generations of adjustable loop buttons (ALB) showed increased construct elongation under cyclic loading, which might lead to construct failure of anterior cruciate ligament reconstruction (ACLR). The purpose of this study was to compare contemporary versions of ALB regarding their biomechanical primary stability and to compare them to a fixed suture loop (FSL) construct.
In a porcine model of ACL reconstruction, superficial porcine flexor tendons were looped to a diameter of 8 mm and fixed with three different ALB and one FLB (each n = 10) in an 8 mm bone tunnel in porcine tibiae. Implants used were:
1. Infinity™ Button (ConMed, Utica, New York) = Chinese finger trap 1 (CFT1)
2. Tightrope® II RT (Arthrex, Naples, Florida) = Chinese finger trap 2 (CFT2)
3. A-TACK (Karl Storz, Tuttlingen, Germany) = Locked suture loop (LSL)
4. FlippTack (Karl Storz, Tuttlingen, Germany) = Fixed suture loop (FSL)
Cyclic loading for 1000 cycles from 0 to 250 N was applied utilizing an uniaxial testing machine (model Z005, Zwick/Roell, Ulm, Germany), followed by load to failure testing. Elongation, Load to failure, stiffness, and yield load of the tested constructs was determined.
After 1000 cycles at 250 N Elongation was 5,0 mm ± 0,8 in the CFT1 group, 4,4 mm ±0,4 in the CFT2 group, 4,9 mm ±1,0 in the LSL group, and 4,8 mm ± 0,8 in the FSL group. No significant differences between the groups were observed. Load to failure was 797 N ± 70 in the CFT1 group, 853 N ±111 in the CFT2 group, 752 N ±129 in the LSL group, and 830 N ± 80 in the FSL group. No significant differences between the groups were observed. Yield load was 570 N ± 25 in the CFT1 group, 563 N ±71 in the CFT2 group, 562 N ±53 in the LSL group, and 560 N ± 57 in the FSL group. No significant differences between the groups were observed.
Contemporary ALB devices do not show significant differences, attributable to implant design and in comparison, to a FSL device. Therefore, regarding biomechanical properties, all tested implants can be used for ACLR.