Biomechanical Comparison of Transosseous Knotless Rotator Cuff Repair Versus Transosseous Equivalent Repair: Half The Anchors With Equivalent Biomechanics?

To compare the biomechanics of a transosseous equivalent (TOE) repair using medial and lateral anchors with tape to a transosseous knotless (TOK) tape repair with only laterally placed intraosseous anchors. One of 2 different repairs were performed on 8 paired specimens: (1) transosseous equivalent (TOE) tape repair or (2) transosseous knotless (TOK) tape repair. Specimens were mounted on a materials testing machine and loaded in uniaxial tension to measure cyclic construct gap formation, followed by failure testing. Paired t tests were used to compare gapping, ultimate stiffness, and failure loads. Fisher exact test was used to compare modes of failure (soft tissue failure vs construct failure). Peak cyclic gapping, failure stiffness, and ultimate failure loads did not differ between TOE and TOK repairs (P = .140 for gapping, P = .106 for stiffness, and P = .672 for peak failure loads). All TOK repairs failed via soft tissue failure medial to the medial suture line, with no construct failures. TOE repairs failed more often through construct failure (anchor migration or suture-bone interface cut through) than TOK repairs (P = .026). TOK repairs only failed through soft tissue whereas TOE repairs failed through both soft tissue and the repair construct. Despite 50% fewer suture anchors in the TOK repairs than the TOE repairs, cyclic gapping and ultimate stiffness and failure loads were not significantly different. The transosseous knotless construct presented is a 2-anchor construct that is equivalent in biomechanical function to a traditional 4-anchor construct, reducing anchor load in the tuberosity.