Knotless Versus Knotted Suture Bridge for Rotator Cuff Tears: A Biomechanical and Histological Study in an Animal Model

BACKGROUND: Knotted suture bridge repair (KSB) has been widely demonstrated as an effective method for rotator cuff tears. However, it is associated with high retear rates, primarily attributed to medial row failure resulting from knot-induced stress concentration and compromised tendon perfusion. Knotless suture bridge repair (KLSB) has recently gained considerable attention as a promising alternative technique. Currently, no consensus exists regarding the necessity of medial row knot tying in suture bridge repair for rotator cuff tears. This study aimed to compare the histological and biomechanical outcomes between KLSB and KSB for rotator cuff repair. HYPOTHESIS/PURPOSE: KLSB will yield superior histological tendon-to-bone healing as compared with KSB. The purpose was to compare the biomechanical and histological outcomes of KLSB and KSB for rotator cuff tears in a rabbit model. STUDY DESIGN: Controlled laboratory study. METHODS: Acute bilateral supraspinatus tears were created in the shoulders of 56 New Zealand White rabbits. KLSB and KSB procedures were randomly assigned to the left or right shoulder. Sixteen animals were euthanized at 2, 4, and 8 weeks postoperatively, with 8 rabbits allocated to histological evaluation and the remaining 8 to biomechanical testing. An additional 8 animals were utilized exclusively for initial biomechanical evaluation at week 0. RESULTS: Macroscopic examination revealed secure reattachment of all repaired tendons to the footprint on the greater tuberosity, with no evident postoperative complications observed at 8 weeks. The KLSB group exhibited significantly enhanced histological tendon-to-bone integration as compared with the KSB group, particularly in fibrocartilage regeneration, collagen composition, and fiber organization at 4 and 8 weeks. Biomechanically, the KSB group demonstrated superior performance in ultimate load to failure and stiffness at 0, 2, and 4 weeks. By 8 weeks, however, no significant differences were detected between the groups. CONCLUSION: Both repair techniques are effective. KSB provides superior early biomechanical performance, whereas KLSB demonstrates distinct advantages in histological healing. Over time, the enhanced healing achieved with KLSB compensates for initial biomechanical deficits, ultimately matching the biomechanical performance of KSB. CLINICAL RELEVANCE: This animal study suggested that KLSB could serve as an alternative option for treating rotator cuff tears in humans, with the possibility of enhancing tendon-to-bone healing. Further research is needed to confirm its applicability.