The Number of Loaded Sutures Alter the Suture-holding Strength in Different Knotless Suture Anchors: A Biomechanical Study

Background: Due to advances in arthroscopic rotator cuff repair, a knotless suture anchor is expected to hold more than two suture limbs. The objective of this study is to investigate whether when employing different fixation mechanisms, the suture-holding strength of knotless anchors are altered by the number of loaded sutures. Objectives: To evaluate the impact of different fixation mechanisms on the suture-holding strength of knotless anchors when varying the number of loaded sutures. Materials and Methods: Three types of knotless anchors (spiral core clamping, winged clamping, and spooling) were tested, with each anchor double-loaded or quadruple-loaded. Cyclic loading was applied, followed by a tensile load until failure. Clinical failure load was defined by 3 mm slippage. A two-way ANOVA was performed to examine the effects of suture anchors and suture number. Results: The two-way ANOVA revealed a significant interaction between the type of suture anchor and the number of sutures ( P < 0.001). Specifically, increasing the number of sutures enhanced the suture-holding strength for the spiral core clamping anchor and the winged clamping anchor ( P < 0.001 for both). Conversely, the spooling anchor did not show any improvement in suture-holding strength with an increased number of sutures. Conclusions: The suture-holding strength of knotless suture anchors is influenced by the number of loaded sutures, with quadruple-loaded spiral core and winged clamping anchors outperforming double-loaded ones, while the spooling anchor shows no improvement.