Background: When tying knots, some surgeons do not pay particular attention to the direction in which they pull to lay down throws. We examine to what extent does pulling direction influence on knot security.
Methods: A total of 368 residents were instructed to tie knots with from 2 to 7 throws using silk braided suture in 3-0 gauge. The direction in which they pulled to lay down throws was recorded. Only the knots tied either by pulling in alternate directions (Group A) or in constant direction (Group C) from the first throw to the last were involved in statistical analysis. Tensile strength and untying rate of the knots were then measured for comparative analysis.
Results: For knots with from 2 to 7 throws, the tensile strength of the ones from Group A was significantly higher than that of the ones from Group C (p < 0.05), respectively. For knots with from 5 to 7 throws, the untying rate of the ones from Group A was significantly lower than that of the ones from Group C (p < 0.05), respectively. For the unraveled knots with from 2 to 7 throws (except for the ones with 5 throws), the tensile strength of the ones from Group A was significantly higher than that of the ones from Group C (p < 0.05), respectively.
Conclusion: Pulling in constant direction results in inferior knot security. Surgeons must ascertain the influence of pulling direction on knot security, and try to achieve superior security with fewer throws to ensure patient safety.
Keywords: Knot security; Knot tying; Pulling direction; Tensile testing.
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