Differences of tensile strength in knot tying technique between orthopaedic surgical instructors and trainees

Knot tying technique is an extremely important basic skill for all surgeons. Clinically, knot slippage or suture breakage will lead to wound complications. Although some previous studies described the knot-tying technique of medical students or trainees, little information had been reported on the knot-tying technique of instructors. The objective of the preset study was to assess surgeons' manual knot tying techniques and to investigate the differences of tensile strength in knot tying technique between surgical instructors and trainees.

A total of 48 orthopaedic surgeons (postgraduate year: PGY 2-18) participated. Surgeons were requested to tie surgical knots manually using same suture material. They were divided into two groups based on each career; instructors and trainees. Although four open conventional knots with four throws were chosen and done with self-selected methods, knot tying practice to have the appropriate square knots was done as education only for trainees before the actual trial. The knots were placed over a 30 cm long custom made smooth polished surface with two cylindrical rods. All knots were tested for tensile strength using a tensiometer. The surgical loops were loaded until the knot slipped or the suture broke. The tensile strength of each individual knot was defined as the force (N) required to result in knot failure. Simultaneously, knot failure was evaluated based on knot slippage or suture rupture. In terms of tensile strength or knot failure, statistical comparison was performed between groups using two-tailed Mann-Whitney U test or Fisher exact probability test, respectively.

Twenty-four instructors (PGY6-PGY18) and 24 trainees (PGY2-PGY5) were enrolled. Tensile strength was significantly greater in trainees (83.0 ± 27.7 N) than in instructors (49.9 ± 34.4 N, P = 0.0246). The ratio of slippage was significantly larger in instructors than in trainees (P < 0.001). Knot slippage (31.8 ± 17.7 N) was significantly worse than suture rupture (89.9 ± 22.2 N, P < 0.001) in tensile strength.

Mean tensile strength of knots done by trainees after practice was judged to be greater than that done by instructors in the present study. Clinically, knot slippage can lead to wound dehiscence, compared to suture rupture.