Comparison of Physical Properties of Polypropylene Sutures and Knot Method to Prevent the Slippage of Sutured Scleral Fixation

Purpose: This study compared the physical properties of 9-0 and 10-0 polypropylene sutures used in scleral-sutured posterior chamber intraocular lens (PCIOL) fixation, with a focus on knot security and methods to prevent slippage.Methods: Tensile strength measurements were performed on 10-0 and 9-0 polypropylene sutures (Prolene<sup>™</sup>) using a material testing machine (Instron 5966 Load Frame, Model 2701-065 controller; Instron Corp., Norwood, MA). Various knotting techniques were evaluated, including a single fisherman’s knot and one, three, and five overhand knots tied around the haptic of a three-piece IOL. Knot thickness and area of the surgeon’s Knot were measured using microscopy and Image J<sup>®</sup> software, with statistical analysis conducted to compare the differences between the two suture types.Results: The 9-0 polypropylene sutures exhibited a significantly higher maximum tensile strength than the 10-0 sutures, particularly with a single fisherman’s knot (0.47 N vs. 0.52 N, <i>p</i> = 0.007; 0.27 N vs. 0.50 N, <i>p</i> < 0.001). However, when multiple overhand knots were tied around the haptic, the 10-0 sutures showed increased tensile strength with more knots (0.11 N, 0.23 N, 0.33 N, <i>p</i> < 0.05), whereas the 9-0 sutures did not (0.06 N, 0.31 N, 0.19 N). Notably, three overhand knots provided better stability than five knots (<i>p</i> < 0.05). The knot area and thickness of the surgeon’s knot were significantly larger in the 9-0 sutures than in the 10-0 sutures (21,062.4 μm<sup>2</sup> vs. 41,188.5 μm<sup>2</sup>, <i>p</i> < 0.001; 160.1 μm vs. 195.6 μm, <i>p</i> = 0.021).Conclusions: Overhand knots increased friction between the suture and IOL haptic, enhancing knot security. However, in the 9-0 sutures, the higher rigidity caused the knots to loosen more easily, decreasing the tensile strength with more knots. This study suggests that three overhand knots are optimal for securing IOL haptics using both 9-0 and 10-0 sutures.