Rotator cuff tears have an estimated incidence of 3.7 per 100,000 individuals per year, with peak occurrence during the 5th decade in men and 6th decade for women. Greater than 300,000 repairs are performed each year, with observed retear rates ranging from 25% to 90%. Successful surgical outcomes are dependent upon both intrinsic musculotendinous properties (e.g., architectural, biomechanical, and healing capacity) as well as the surgical repair technique. In chronic tendon ruptures, repair becomes more technically difficult due to irreversible architectural changes in the musculotendinous unit, including fatty infiltration, muscle fiber shortening and increased muscle pennation angle.
Prior laboratory studies have suggested that superior initial fixation strength, tendon to bone footprint contact and stability under cyclic loading may lead to improved repair outcomes. Despite some conflicting reports, biomechanical results generally indicate that multi-row and transosseous-equivalent configurations confer improved fixation relative to single-row techniques. Technical developments such as double-row and transosseous- equivalent repairs increase pressurized contact at the insertion footprint but necessitate additional anchors and sutures. Furthermore, the latter findings are derived from cadaveric studies utilizing tendon detachment, immediate repair, and mechanical testing of tendon– suture–anchor–bone constructs. In contrast, little attention has focused on suture retention properties of the medial and lateral regions of the tendon (independent of fixation technique) in both intact and torn states. An improved understanding of supraspinatus tendon regional collagen fiber functional and architectural properties may provide additional guidance with regard to intraoperative suture placement during rotator cuff repair. Therefore, the present investigation evaluated the mechanical capacity of intact and torn human supraspinatus tendons to retain a suture with both lateral and medial placements. As tears typically propagate from the insertion site, we hypothesized that torn tendons and specifically the lateral region would exhibit inferior suture retention and ultrastructural properties compared to intact specimens. In addition, collagen fibril and immunohistochemical characteristics were examined to provide additional insight into structure-function relationships.