Original Article| Volume 35, ISSUE 1, P70-76.e1, January 2019

Knotless Anchors in Acetabular Labral Repair: A Biomechanical Comparison

Published:November 22, 2018DOI:


      To analyze the failure mechanism, stiffness, and pullout strength of acetabular knotless suture anchors.


      Seven suture anchors were tested in high-density (0.48 g/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 1 mm/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 2.9 mm served as a baseline for comparison.


      Stiffness was highest in the Pushlock, the SpeedLock HIP, and Knotilus. At 1 mm 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).


      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 1 mm 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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      Linked Article

      • Editorial Commentary: Acetabular Labral Repair—Is A Knotless Anchor Better?
        ArthroscopyVol. 35Issue 1
        • Preview
          Knotless anchors have an important role in arthroscopic acetabular labral repair. Different anchors show 2 primary failure modes: suture breakage and suture pullout from the anchor (“eyelet failure”). Knotless anchors show minimal displacement at physiological loads and should perform well for arthroscopic labral repair. Surgeons should consider the suture-passing device size and use a device that creates as small of a labral hole as possible.
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