Knotless Fixation Is Stronger and Less Variable Than Knotted Constructs in Securing a Suture Loop

BACKGROUND: Historically, tendon-to-bone fixation has relied on knot tying. However, considerable variability exists in knot-tying strength among surgeons. PURPOSE/HYPOTHESIS: The purpose of this study was to compare the biomechanical properties of knotted and knotless fixation and to evaluate variability among surgeons. The hypothesis was that knotless constructs would be stronger and have less variability as compared with knotted constructs. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 34 orthopaedic surgeons participated in a laboratory study to compare knotted and knotless constructs, where 104 knotted constructs were performed with No. 2 suture, 21 knotless constructs with No. 2 suture (K2 group), and 79 knotless constructs with suture tape (KT group). Mechanical testing was performed to compare load at 3 mm of displacement, load to failure, and stiffness of each construct. RESULTS: The mean load at 3 mm of displacement was greatest in the KT group, with significant differences among all 3 groups (P < .001). Load to failure was significantly greater in the KT group as compared with the K2 group and the knotted group (P < .001), but there was no difference between the K2 and knotted groups (P ≥ .999). Stiffness and displacement were also greatest in the KT group. Based on the F test, the variance in load to failure was significantly different between the knotted and knotless constructs, with the knotted group demonstrating greater variability (SD, 94 N) than the KT (SD, 38 N) and K2 (SD, 17 N) groups (P < .001). CONCLUSION: Knotless fixation with suture tape had improved biomechanical performance as compared with knots or knotless fixation with No. 2 suture. In addition, knotless fixation had less variability in biomechanical properties among multiple surgeons. CLINICAL RELEVANCE: This study may be relevant for surgeons choosing between knotted and knotless constructs as well as for considerations in the design of rotator cuff repair constructs.