Design of vessel ligation simulator for deliberate practice

Background Surgical residents develop technical skills at variable rates, often based on random chance of cases encountered. One such skill is tying secure knots without exerting excessive force. This study describes the design of a simulator using a force sensor to measure instantaneous forces exerted on a blood vessel analog during vessel ligation and the development of expert-derived performance goals. Materials and methods Vessel ligations were performed on Silastic tubing at an offset from a Vernier Force Sensor. Nine experts (surgical faculty and senior residents) and 10 novices (junior residents) were recruited to each perform 10 vessel ligations (two square knots each) with two-handed and one-handed techniques. Internal consistency for the series of vessel ligations was tested with Cronbach alpha. Maximum forces exerted by novices and experts were compared using Student t-test. Results Internal consistency across the 10 ligations on the simulator was excellent (Cronbach alpha = 0.91). The expert group on average exerted a significantly lower maximum force when compared with novices while performing two-handed (0.76 ± 0.39 N versus 1.12 ± 0.49 N, P < 0.01) and one-handed (0.84 ± 0.32 N versus 1.36 ± 0.44 N, P < 0.01) vessel ligations. Conclusions Although the expert group performed vessel ligations with significantly lower peak force than the novice group, there were novices who performed at the expert level. This is consistent with the conceptual framework of milestones and suggests that the skill of gentle knot-tying can be measured and develops at different chronologic levels of training in different individuals. This simulator can be used as part of a deliberate practice curriculum with instantaneous visual feedback.