Influence of direction of view, target-to-endoscope distance and manipulation angle on endoscopic knot tying

The aim of the study was to investigate the influence of (1) the direction of view of the endoscope, (2) the endoscope-to-task distance and (3) the manipulation angle between the instruments on intracorporeal endoscopic knotting.

Rigid endoscopes (0 degree, 30 degrees and 45 degrees) were introduced with the objective set at distances of 50, 75, 100, 125 and 150 mm from the task. Needle holders were inserted to make 30 degrees, 60 degrees and 90 degrees manipulation angles. The execution time and knot quality parameters of 2700 knots performed by ten surgeons were obtained.

There was no significant difference in the execution time or parameters of knot quality with different endoscopes. The longest execution time (median 95 s, P < 0.0001) and the lowest performance quality score (20.61, P < 0.001) were observed at a distance of 50 mm when compared to other distances. A 60 degrees manipulation angle had a shorter execution time (median 71 s, P < 0.0001) and a higher performance quality score (26.84, P < 0.0001) than either 30 degrees or 90 degrees manipulation angles.

The direction of view of the endoscope had no significant effect on intracorporeal knotting if the optical axis subtended the same angle with the task surface. The optimal ergonomic conditions include an endoscope-to-target distance of 75-150 mm and a manipulation angle of 60 degrees.