Anatomic Knot Suture Anchor Versus Knotless Suture Anchor Technique for Anterior Talofibular Ligament Repair: A Biomechanical Comparison

BACKGROUND: To date, there are few biomechanical studies comparing the strength between knot repair and knotless repair procedures for anterior talofibular ligament (ATFL) injury. PURPOSE: To perform a biomechanical comparison of the strength of the arthroscopic ATFL repair technique with knot or knotless suture anchors in a cadaveric model with partial or complete ATFL injuries. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 24 fresh-frozen cadaveric ankles were used. Arthroscopy was used to identify, section, and repair the ATFL on the fibular insertion site. The specimens were then randomly placed into 1 of 4 groups: group A received complete ATFL section and 1–suture anchor repair with knot, group B received complete ATFL section and 1-anchor knotless repair, group C received partial ATFL section and 1–suture anchor repair with knot, and group D received partial ATFL section and 1-anchor knotless repair. After repair, the ATFL tension was measured first with a digitalized tensiometer. Specimens were then mounted on a materials testing system to determine the ultimate load to failure and stiffness. RESULTS: The mean ± SD ligament tension measured during the arthroscopic procedure was 8.6 ± 0.6 N for group A, 9.2 ± 0.5 N for group B, 9.4 ± 1.1 N for group C, and 9.6 ± 0.9 N for group D. No significant difference in tension was detected among groups. In load-to-failure testing, the mean ultimate failure load was 27.9 ± 4.1 N for group A, 26.2 ± 9.3 N for group B, 81.9 ± 26.5 N for group C, and 88.1 ± 41.6 N for group D. The mean ultimate failure loads of the partial repair groups were significantly higher than those of the complete repair groups (C vs A, P = .008; D vs B, P = .002), while there was no significant difference between groups A and B (P > .05) or between groups C and D (P > .05). CONCLUSION: The results of the present study showed that there was no significant difference in biomechanical properties between knot repair and knotless repair techniques. CLINICAL RELEVANCE: Biomechanically, the results showed that knot suture anchor and knotless suture repair provide similar biomechanical strength for ATFL injury. Unfortunately, these methods in the complete ATFL section models provided less than half the strength and stiffness in the partial ATFL section models at time zero after surgery. As a result, 1–suture anchor repair is not suitable for complete ATFL injury regardless of the repair method.