Real-Time Objective Assessment of Knot Quality With a Portable Tensiometer Is Superior to Execution Time for Assessment of Laparoscopic Knot-Tying Performance

Abstract

Objective: Laparoscopic intracorporeal knot tying is a difficult skill to acquire. Currently, time to complete a knot is the most commonly used metric to assess the acquisition of this skill; however, without a measure of knot quality, time is a poor indicator of skills mastery. Others have shown that knot quality can be accurately assessed with a tensiometer, but obtaining this type of assessment has typically been cumbersome. We investigated a new method of real-time assessment of knot quality that allows for more practical use of knot quality as a performance metric. Methods: Eleven experienced endoscopic surgeons tied 100 intracorporeal knots in a standard box trainer. Each of the knots was immediately tested using the InSpec 2200 benchtop tensiometer (INSTRON, Canton MA) where a knot quality score (KQS) is generated based on the load handling properties of the knotted suture. The execution time was also recorded for each knot. Results: The assessment of all knots ended with one of two end points: knots that slipped (n = 48)or knots that held until the suture broke (n = 52). Knots that slip are generally of poorer quality than those that held. Execution time did not correlate with knot-quality score (r= 0.009, P= .9), and the mean execution time did not differ significantly between slipped and held knots (65 vs 68 seconds, P= .8). No completion time criteria were able to accurately predict slipped versus held knots. The mean KQS difference between held and slipped knots was highly significant (24 vs 12, P< .0001). A knot with a KQS exceeding 20 was nearly 10 times more likely to hold than slip. Conclusion: Time to complete a knot is a poor metric for the objective assessment of intracorporeal knot-tying performance in the absence of a measure of knot quality. Real-time evaluation of the knot quality can accurately distinguish welltied knots from poorly tied knots. This mode of assessment should be incorporated into training curriculum for surgical knot tying.