Biomechanical Analysis of Anteroinferior Bankart Repair Anchor Types.

BACKGROUND: All-suture anchors and knotless anchors are increasingly used in the repair of anteroinferior labral tears in patients with shoulder instability. Optimal repair constructs may limit recurrent instability. PURPOSE: To perform a quantitative biomechanical comparison of 3 labral fixation devices for soft tissue Bankart lesions: knotless soft-body tensionable anchor (SB knotless), knotted soft-body anchor (SB knotted), and knotless hard-body PEEK (polyether ether ketone) interference anchor (HB knotless). STUDY DESIGN: Controlled laboratory study. METHODS: A total of 21 glenoid specimens were randomized into 3 groups: SB knotless, SB knotted, and HB knotless. Artificial Bankart lesions were created at the anteroinferior labrum. Anchors were placed at the 3:30, 4:30, and 5:30 clockface positions, and sutures were passed through 1 cm of tissue. Anchors were tested simultaneously as one construct by pulling capsular tissue connected to the anteroinferior quadrant. Cyclic loading (5-25 N, 100 cycles) was followed by load-to-failure testing (15 mm/min). Biomechanical testing variables were collected, and failure mechanisms were recorded per individual anchor. RESULTS: There were no differences in baseline specimen characteristics. There was no difference in elongation during cyclic loading (P = .40). The ultimate load to failure between SB knotless (309.7 ± 125.6 N), SB knotted (226.4 ± 34.8 N), and HB knotless (256.5 ± 90.5 N) did not significantly differ (P = .25). Failure mechanisms differed among groups (P = .008); mechanisms included anchor pullout (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 method failure, defined as knot failure for knotted anchors or locking mechanism failure for knotless anchors (SB knotless: 0.0%; SB knotted: 38.1%; HB knotless: 38.1%).). CONCLUSION: The SB knotless, SB knotted, and HB knotless labral fixation anchors studied exhibited comparable elongation during cyclic loading, stiffness, and ultimate loads to failure in a cadaveric model. However, the failure mechanisms significantly differed, as SB knotless anchors failed primarily from suture pull-through, while SB knotted and HB knotless anchors were subject to knot failure and locking mechanism failure, respectively. CLINICAL RELEVANCE: These data support the benefit of SB knotless anchors for anteroinferior labral repair in limiting knot failure typically seen with knotted anchors, perhaps demonstrating that all-suture anchors may have better locking mechanism quality than their PEEK counterparts.

Biphasic Interpositional Allograft for Rotator Cuff Repair Augmentation Is Safe in an Ovine Model.

PURPOSE: To perform a preclinical histologic assessment of a biphasic acellular interpositional cancellous allograft in an ovine model of rotator cuff repair (RCR) designed to better understand its safety profile and effects on tendon healing after RCR. METHODS: Thirty skeletally mature sheep with clinically normal shoulders with an artificially created degenerative infraspinatus tendon tear were randomized to control and treatment groups. Animals were euthanized at 3 weeks, 6 weeks, and 12 weeks. After gross dissection, rotator cuff specimens were fixed with formalin and polymerized for sectioning and staining. Blinded histologic scores evaluated inflammatory cell infiltrates, signs of degradation, particulate debris, collagen arrangement, neovascularization, and enthesis qualitative measures. RESULTS: There were no treatment specimens that exhibited histologic signs of a significant infection, inflammatory infiltrate, or foreign body reaction such as granuloma or fibrous capsule formation. Histologic scores in all categories were not significantly different at all time points, including the primary end point mean cumulative inflammatory score (control: 3.66 ± 1.21 vs treated: 4.33 ± 1.51, P = .42), when comparing the treatment and control RCR groups. In general, the degree of tendon healing and host tissue response was essentially equivalent between the 2 groups with observation of low overall levels of inflammation and progressive improvements in collagen organization, reduced tenocyte activity, and fibrocartilaginous enthesis reformation. CONCLUSIONS: This histologic study demonstrated the use of a biphasic interpositional allograft for RCR augmentation in an ovine model does not generate an inflammatory response or foreign body reaction. Use of the biphasic interpositional allograft resulted in a histological profile that was essentially equivalent to that of a standard RCR at 3-, 6-, and 12-week postoperative timepoints. These findings suggest that a biphasic interpositional allograft is safe for further clinical investigation in humans before broader clinical application. CLINICAL RELEVANCE: Patch augmentation of RCR is a popular technique that has shown clinical success in improving the likelihood of a successful repair in patients at elevated risk for retear. Newer augmentation technologies are being developed to address the biology at the interface between the bone and soft tissue where failure typically occurs.