Biomechanical Investigation of Different Tying Forces on Knot Security

Abstract

Background: Knowing the relationship between tying force and knot security could reduce knot failure due to inconsistent tying forces. This study presents a new experimental set-up that enables testing of a knot configuration tied with a measured force.Methods: Five tying forces 1N, 2N, 3N, 4N, 5N were investigated. The surgeon's knot with 3 throws (2-1-1) was used to suture two 70x15mm porcine skins together with Prolene 4.0. Ten specimens were involved in each group. The specimen was subjected to 2 stages of cyclic testing of 200 cycles. Stage I was subjected to a cyclic load of 2N-10N and Stage II, a cyclic load of 2N-20N. Survival rate of the knots for each stage was calculated. Knots that survived were subjected to static testing. Ultimate tensile strength (UTS) required to cause knot failure was recorded.Results: 3±0.5N tying force had the highest survival rate of 100% in stage I and 90% in stage II. This result contradicted static testing results which showed that tying forces between 3N to 5N could achieve the highest UTS without statistically significance. Another finding was that knots tied with different tying forces behave independently under various cyclic loading conditions. Conclusion:A new experimental setup to test a knot configuration with different tying force was presented. Based on static and cyclic testing, we found that 3±0.5N is the optimum force needed to tie a surgeon's knot with 3 throws for maximal knot security using Prolene 4.0.