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

Abstract

Background: It is not clear whether the mechanical strength of adjustable-loop suspension devices (ALDs) in anterior cruciate ligament (ACL) reconstruction is device dependent and if these constructs are different from those of an interference screw. Purpose: To compare the biomechanical differences of 2 types of ALDs versus an interference screw. Study Design: Controlled laboratory study. Methods: ACL reconstruction was performed on porcine femurs and bovine extensor tendons with 3 types of fixation devices: interference screw, UltraButton (UB) ALD, and TightRope (TR) ALD (n = 10 for each). In addition to specimen testing, isolated testing of the 2 ALDs was performed. The loading protocol consisted of 3 stages: preload (static 150 N load for 5 minutes), cyclic load (50-250 N at 1 Hz for 1000 cycles), and load to failure (crosshead speed 50 mm/min). Displacement at different cycles, ultimate failure load, yield load, stiffness, and failure mode were recorded. Results: In specimen testing, displacement of the ALDs at the 1000th cycle was similar (3.42 ± 1.34 mm for TR and 3.39 ± 0.92 mm for UB), but both were significantly lower than that of the interference screw (7.54 ± 3.18 mm) ( P < .001 for both). The yield load of the UB (547 ± 173 N) was higher than that of the TR (420 ± 72 N) ( P = .033) or the interference screw (386 ± 51 N; P = .013), with no significant difference between the latter 2. In isolated device testing, the ultimate failure load of the TR (862 ± 64 N) was significantly lower than that of the UB (1879 ± 126 N) ( P < .001). Conclusion: Both ALDs showed significantly less displacement in cyclic loading at ultimate failure than the interference screw. The yield load of the UB was significantly higher than that of the other 2. The ultimate failure occurred at a significantly higher load for UB than it did for TR in isolated device testing. Clinical Relevance: Both UB and TR provided stronger fixation than an interference screw. Although difficult to assess, intrinsic differences in the mechanical properties of these ALDs may affect clinical outcomes.

Comparison of Time-Zero Primary Stability Between a Biodegradable Magnesium Bone Staple and Metal Bone Staples for Knee Ligament Fixation: A Biomechanical Study in a Porcine Model

“…The anatomy of porcine knees was shown to be sufficiently similar to that of human knees, 46 and porcine flexor tendons possess biomechanical properties similar to those of human hamstring tendons, 17 making it a frequently used model to assess the biomechanical primary stability of orthopaedic implants. 19,23,24,43 Nevertheless, bone density in the porcine model is significantly higher in comparison with humans, 1 which could have affected the findings of the present study. 8,42 A recent study showed that, in a test setup like that used in this study, the displacement of the machine actuator used to calculate the elongation was significantly higher than the actual graft slippage, as measured by optical tracking at the tunnel aperture, although both values were highly correlated.…”

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

“… 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. Second, in numerous biomechanical studies, cyclic loading was performed without complete unloading.…”

Clinical and Radiological Outcomes in Patients With Anterior Shoulder Instability and Glenoid Bone Loss after Arthroscopic Free Bone Block Combined With Dynamic Anterior Stabilization

“…In this study, we modified the LHBT fixation technique to the adjustable loop suspensory system, which allowed enough tendon-to-bone contact inside the glenoid tunnel and provided greater mechanical strength. 30…”

“…In this study, we modified the LHBT fixation technique to the adjustable loop suspensory system, which allowed enough tendon-tobone contact inside the glenoid tunnel and provided greater mechanical strength. 30 Bone resorption during the graft remodeling phase weakens the bone-mediated biomechanical effect on anterior shoulder stability, especially with allografts. 57,60 In 2 recent studies using iliac crest bone allografts, Boehm et al 9 reported nearly complete bone resorption in all patients with only a 2.2% glenoid defect decrease at 1year follow-up, Russo et al 56 observed that 10 of 19 patients had complete bone resorption.…”