Surgical Knot Strength in Continuous Wound Closures

Background: Forces applied to knots used for interrupted vs. continuous closures are very different. We studied the knot strength and knot security of three knots when simulating a continuous wound closure: the square, the sliding, and a hybrid constructed using a surgeon’s square knot followed by a sliding knot. Materials and Methods: Knot holding capacity (KHC) of single-strand 1-0 polypropylene was determined by slow distraction on a horizontal testing sled of the strand that would be used to complete a continuous (“running”) closure following placement of an anchoring knot with six throws. Distraction continued until failure of the knot defined as breakage or slippage of the knot. Results: The mean and standard deviation of KHC measured in pounds was determined (n = 30 for each knot): standard square 8.94 +/– 1.04; sliding 10.72 +/– 1.35; and hybrid 10.95 +/– 1.10. For each knot the relative knot security [(KHC of the knot/Tensile strength of untied strand) × 100] was calculated: standard square 69.5%; sliding 83.4%; hybrid 85.2%. Significant differences (p < 0.0001) in KHC exist between square and sliding knots (favoring sliding knots) and between square and hybrid knots (favoring hybrid knots). Hybrid and sliding knots were not statistically different. Conclusions: Sliding knots and hybrid knots are superior to square knots as anchoring knots for single-strand continuous wound closure.