Mechanical testing of different knot types using high-performance suture material.

Abstract

This laboratory study aimed to evaluate the loop security, knot security, cyclic loading resistance and load-to-failure rate of three different knot types with establishing a new experimental set-up. Additionally, the mode of failure of each knot was evaluated. With the use of nonabsorbable, braided polyethylene sutures, USP size No. 2 [Hi-Fi^®; ConMed Linvatec], the arthroscopic knot types Dines, SMC as well as the surgeon's knot were tested using a material testing machine. The knots were tied openly as well as arthroscopically. The set-up enables testing of knot configurations while eliminating friction between knot loop and its suspension points. Including all test procedures, a total of 216 knots were tested. All openly tied knot types and ten of each type of arthroscopically tied knots resisted against cyclic loading of 1,000 cycles. With subsequent load-to-failure testing, openly tied knot types achieved significantly higher values of tensile strength than arthroscopically tied knots. Regarding clinical failure, defined as an elongation of 3 mm, Dines knot reached highest loop as well as knot security. Knot slippage was the most common failure mechanism at an elongation of 3 mm, whereas suture breakage was evaluated most at an elongation of 6 mm. The new experimental set-up confirms the loop security of arthroscopic knot types. Using a knot pusher clinically is a key factor to attain this as compared to openly hand-tied techniques. The Dines knot presented the highest reliability. It may provide a secure tissue healing during rehabilitation and consequently can be recommended for clinical application.