Effect of intracorporeal-extracorporeal instrument length ratio on endoscopic task performance and surgeon movements

Hypothesis: Better endoscopic task performance and more ergonomic movements of a surgeon's dominant upper limb can be achieved within a certain range of intracorporeal-extracorporeal instrument length ratio. Design: Investigating the effect of 3 intracorporeal-extratorporeal instrum ent length ratios (240:120 mm, level 1; 180:180 mm, level 2; and 120:240 mm , level 3) an efficiency and quality of a standardized endoscopic task (int racorporeal surgeon's knot). Ten surgeons tied 360 knots inside a trainer i n a random sequence. Task efficiency was measured by the execution time, wh ich was recorded for each knot. Task quality was measured by the knot quali ty score, derived from the force-extension curves obtained by distraction o f each knot in a tensiometer. Motion analysis parameters were obtained at t he elbow and shoulder joints using a 3-dimensional motion analysis system ( Kinemetrix Model 5.0-3D/3MBM; Medical Research Ltd, Leeds, England). The Kr uskal-Wallis and Mann-Whitney tests were used for analysis. Results: The level 3 ratio had the lon est knot quality score (P = .07) and longest execution time (P<.05). The range of movement at the elbow was sig nificantly greater with the level 3 ratio than with the level 1 ratio (P<.0 5). The level 3 ratio also resulted in the widest range of movement at the shoulder (P<.05 for level 2 vs 3; P = .06 for lever 1 vs 3). The median ang ular velocity was 329.5 degrees/s, 360 degrees/s, and 530 degrees/s for lev els 1, 2, and 3, respectively (P = .10). Conclusions: Intracorporeal-extracorporeal instrument length ratio below 1. 0 degrades task performance and is associated with a wider range of movemen t at the elbow and shoulder and a higher angular velocity at the shoulder.