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. 2024 Apr 3;12(4):23259671241240375.
doi: 10.1177/23259671241240375. eCollection 2024 Apr.

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

Adrian Deichsel  1 , Lara Leibrandt  1 , Michael J Raschke  1 , Matthias Klimek  1 , Simon Oeckenpöhler  1 , Elmar Herbst  1 , Christoph Kittl  1 , Johannes Glasbrenner  1
Affiliations

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

Adrian Deichsel et al. Orthop J Sports Med. .

Abstract

Background: Concerns regarding the primary stability of early adjustable loop button (ALB) devices for cortical fixation of tendon grafts in anterior cruciate ligament reconstruction (ACLR) have led to the development of new implant designs.

Purpose: To evaluate biomechanical stability of recent ALB implants in comparison with a continuous loop button (CLB) device.

Study design: Controlled laboratory study.

Methods: ACLR was performed in a porcine model (n = 40) using 2-strand porcine flexor tendons with a diameter of 8 mm. Three ALB devices (Infinity Button [ALB1 group]; Tightrope II RT [ALB2 group]; A-TACK [ALB3 group]) and 1 CLB device (FlippTack with polyethylene suture) were used for cortical tendon graft fixation. Cyclic loading (1000 cycles up to 250 N) with complete unloading were applied to the free end of the tendon graft using a uniaxial testing machine, followed by load to failure. Elongation, stiffness, yield load, and ultimate failure load were recorded and compared between the groups using a Kruskal-Wallis test with post hoc Dunn correction.

Results: Elongation after 1000 cycles at 250 N was similar between groups (ALB1, 4.5 ± 0.7 mm; ALB2, 4.8 ± 0.8 mm; ALB3, 4.5 ± 0.6 mm; CLB, 4.5 ± 0.8 mm), as was load to failure (ALB1, 838 ± 109 N; ALB2, 930 ± 89 N; ALB3, 809 ± 103 N; CLB, 842 ± 80 N). Stiffness was significantly higher in the ALB1 group compared with the CLB group (262.3 ± 21.6 vs 229.3 ± 15.1 N/mm; P < .05). No significant difference was found between the 4 groups regarding yield load. Constructs failed either by rupture of the loop, breakage of the button, or rupture of the tendon.

Conclusion: The tested third-generation ALB devices for cortical fixation in ACLR withstood cyclic loading with complete unloading without significant differences to a CLB device.

Clinical relevance: The third-generation ALB devices tested in the present study provided biomechanical stability comparable with that of a CLB device. Furthermore, ultimate failure loads of all tested implants exceeded the loads expected to occur in the postoperative period after ACLR.

Keywords: ACL reconstruction; adjustable loop button; continuous loop button; cortical fixation.

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Conflict of interest statement

The authors have declared that there are no conflicts of interest in the authorship and publication of this contribution. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Figures

Figure 1.
Figure 1.
Cortical fixation of (A) a soft tissue tendon graft in dual diameter bone tunnel of 40 mm total length with (B) a tendon-to-bone interface of 20 mm length, with the free end of the tendon graft fixed to a material testing machine by a cryoclamp.
Figure 2.
Figure 2.
Details of cortical fixation devices from the front (top row) and back (bottom row): (A) Infinity Button; (B) Tightrope II RT; (C) A-TACK; and (D) custom-made continuous-loop button using a FlippTack with a double-looped and hand-knotted polyethylene suture (No. 2 FiberWire).
Figure 3.
Figure 3.
Results of biomechanical testing for (A) elongation after cyclic loading at 250 N, (B) load to failure, (C) stiffness, and (D) yield load. Boxplots present the mean (horizontal line), standard deviation (top and bottom of the box), and range (whiskers). *Statistically significant difference between groups (P < .05). ALB, adjustable loop button; CLB, continuous loop button.
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