Poster 111: Biomechanical Analysis of Anteroinferior Bankart Repair Anchor Types: Has Technology Surpassed Surgeon Technique?

OBJECTIVES: To limit risk of recurrent dislocation, subsequent injury, and more complex surgeries, it is critical to understand the best techniques to repair a soft-tissue Bankart lesion in the setting of minimal bone loss. To the authors’ knowledge, there is no current biomechanical data comparing tensionable knotless all-suture anchors to knotted all-suture anchors and hardbody knotless anchors in labral repair constructs. Therefore, the purpose of this study was to perform a quantitative biomechanical comparison of three labral fixation devices for soft-tissue Bankart lesions: soft body tensionable knotless anchor (SB knotless), knotted soft body anchor (SB knotted), knotless interference polyetheretherketone (PEEK) hardbody anchor (HB knotless). The authors hypothesized that the three anchor types would exhibit similar biomechanical properties including elongation, failure load, and stiffness but that the SB knotless would display different failure mechanisms from the SB knotted and HB knotless anchors. METHODS: Twenty-one glenoid cadavers were randomized to 3 groups: SB knotless (Arthrex 1.8mm FiberTak Knotless All-suture Anchor), SB knotted (Arthrex 1.8mm FiberTak Knotted single loaded All- Suture Anchor), and HB knotless (Arthrex 2.9mm PushLock Knotless PEEK anchor). The humeral head was disarticulated and artificial Bankart lesions were created at the anteroinferior (AI) labrum. Anchors were placed at the 3:30, 4:30, and 5:30 positions, and sutures were passed through 1cm of tissue (Figure 1). Knotted anchors were tied with five square knots. Anchors were tested simultaneously as one construct by pulling the capsular tissue connected to the AI quadrant. Cyclic loading (5-25 N, 100 cycles) was followed by load-to-failure testing (15mm/min). Mechanical testing variables were collected, and failure mechanisms were recorded per individual anchor. Statistical comparisons were made among groups including ANOVA for normally-distributed continuous variables, Kruskal-Wallis for non- parametric continuous variables, and Fisher’s Exact test for categorical variables. RESULTS: There were no significant differences among groups in cadaveric age (p = 0.43), body mass index (p = 0.42), bone mineral density (p = 0.84), laterality (p = 0.26), or sex (p = 0.098). There was no significant difference between groups in cyclic elongation measured from the first to last cycle during cyclic loading (p = 0.40). Ultimate load to failure between SB knotless (309.7 ± 125.6 N), SB knotted (226.40 ± 34.8 N), and HB knotless (256.5 ± 90.5 N) did not significantly differ (p = 0.25) (Table 1). Failure mechanisms significantly differed among groups; mechanisms included anchor pull-out (SB knotless 33.3%; SB knotted 23.8%; HB knotless 28.6%), suture pull-through (SB knotless 66.7%; SB knotted 38.1%; HB knotless 33.3%), and anchor fixation failure, defined as knot failure for knotted anchors or locking mechanism failure for knotless anchors (SB knotless 0%; SB knotted 38.1%; HB knotless 38.1%, p = 0.008) (Figure 2). CONCLUSIONS: The SB knotless, SB knotted, and HB knotless labral fixation anchors studied exhibit comparable elongation during cyclic loading, stiffness, and ultimate loads to failure. However, the SB knotless anchor avoids the risk of knot failure and interference failure inherent to SB knotted and HB knotless interference anchors, respectively. This data supports the benefit of SB knotless anchors for anteroinferior labral repair in limiting knot failure seen with knotted anchors and perhaps demonstrating that all- suture anchors may have better locking mechanism quality than their PEEK counterpart. How and if these mechanical properties of the anchors correlate with clinical results for soft-tissue Bankart repair requires further investigation, and likely one with high power from multi- center studies to detect if subtle differences exist.