Biomechanical testing of a new knotless suture anchor compared with established anchors for rotator cuff repair

Various suture anchors are available for rotator cuff repair. For arthroscopic application, a knotless anchor was developed to simplify the intra-operative handling. We compared the new knotless anchor (BIOKNOTLESS (TM) RC, DePuy Mitek, Raynham, MA) with established absorbable and titanium suture anchors (UltraSorb (TM) and Super Revo 5mm (TM); ConMed Linvatec, Utica, NY). Each anchor was tested on 6 human cadaveric shoulders. The anchors were inserted into the greater tuberosity. An incremental cyclic loading was performed. Ultimate failure loads, anchor displacement, and mode of failure were recorded. The anchor displacement of the BIOKNOTLESS (TM) RC (15.3 +/- 5.3 mm) after the first cycle with 75 N was significantly higher than with the two other anchors (Super Revo 2.1 +/- 6 mm, UltraSorb: 2.7 +/- 7.7 mm). There was no significant difference in the ultimate failure loads of the 3 anchors. Although the Bioknotless (TM) RC indicated comparable maximal pullout strength, it bares the risk of losing contact between the tendon-bone-interface due to a significantly higher system displacement. Therefore, gap formation between the bone and the soft tissue fixation jeopardizes the repair. Bioknotless (TM) RC should be used in the lateral row only when a double row technique for rotator cuff repair is performed, and is not appropriate for rotator cuff repair if used on its own.