Hand-assisted laparoscopic surgery is associated with enhanced depth perception in novices

The visual information obtained in hand-assisted laparoscopic surgery (HALS) and total laparoscopy is based on two-dimensional depth cues. This study was designed to test the hypothesis that intracorporeal hand improves depth perception in HALS.Ten subjects were divided into two groups using HALS or total laparoscopy. The first task was passing a 10-cm thread through four small metallic loops five times; the second was tying 30 square three-throw intracorporeal laparoscopic knots. End points were (1) number of past pointing as an index of movement accuracy and reflection of depth perception, (2) execution time, and (3) knot quality score.The HALS group was significantly faster than total laparoscopy with a median (interquartile range (IQR)) of 117 s (75.5) vs. 179 s (235.5; P = 0.001) for the thread passing task and 97 s (43.3) vs. 130 s (68.3; P < 0.0005) for knot tying. The number of past-pointing events was significantly lower with HALS compared with total laparoscopy with a median (IQR) of 12 (8) vs. 23 (24; P = 0.001) for the thread passing task and 7 (5) vs. 13 (10; P < 0.0005) for knot tying. There was a significant main effect of whether the targeted object was in contact with the other instrument in knot tying task when past-pointing occurred (P = 0.031). No difference in a knot quality score was found between the HALS and total laparoscopy.The accuracy of instrument movement was significantly better in the HALS group compared with total laparoscopy. The study confirmed the hypothesis that intracorporeal hand improves depth perception in HALS. Also, the touch of the assisting instrument with the target object enhances spatial orientation in the laparoscopic operative field. However, further study is needed to test the hypothesis in experts.