Knotless Anchors in Acetabular Labral Repair: A Biomechanical Comparison. Arthroscopy : the journal of arthroscopic & related surgery : official publication of the Arthroscopy Association of North America and the International Arthroscopy Association Safran, M. R., Behn, A. W., Botser, I. B., Mardones, R. 2018


PURPOSE: To analyze the failure mechanism, stiffness, and pullout strength of acetabular knotless suture anchors.METHODS: Seven suture anchors were tested in high-density (0.48g/cc) synthetic blocks. The anchors were implanted perpendicular to the bone block. The anchor's suture(s) were tied around a loop of 8 high-strength nonabsorbable sutures and pulled in line with the anchor at a rate of 1mm/s until failure. The following knotless anchors were tested: Stryker Knotilus 3.5, Arthrex Pushlock 2.9, Linvatec PopLok 2.8, Linvatec PopLok 3.3, ArthroCare SpeedLock HIP (3.4-mm), and Smith & Nephew Bioraptor Knotless 2.9. The standard knot tying Smith & Nephew Bioraptor 2.9mm served as a baseline for comparison.RESULTS: Stiffness was highest in the Pushlock, the SpeedLock HIP, and Knotilus. At 1mm displacement, the SpeedLock HIP exhibited significantly higher load than all other anchors, excluding the Pushlock and PopLok 3.3 (P=.012 for all comparisons). Excluding the SpeedLock HIP and Knotilus, the Pushlock displayed significantly higher load than all other anchors at 2-mm displacement (P = .015 for all comparisons). Maximum load was the highest for the Knotilus and Bioraptor knotted anchor (P < .001 compared with all other anchors).CONCLUSIONS: All knotless suture anchors used in hip arthroscopy, except for the Knotilus 3.5, failed by suture pullout from the anchor. The 2 anchors with the highest maximum load, the Knotilus 3.5 and knotted Bioraptor 2.9, failed by suture failure; however, these anchors displayed the lowest stiffness and load at 1mm displacement among all anchors tested. Stiffness and loads at clinically relevant displacements, not maximum load alone, may be most important in predicting anchor clinical performance during the early phases of labral healing.CLINICAL RELEVANCE: Knotless suture anchors tend to fail by suture pullout from the anchor, yet the stiffness of these constructs suggests that minimal displacement of the repair will occur under physiologic loads.

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