Mean operation time: 167.54 ± 44.42 minutes (90 - 245): The first group (the initial 30 cases): 194.16 ± 49.52 minutes; The second group (from 31 to 60): 155.67 ± 41.32 minutes; The third group (from 61 to 90): 167.00 ± 36.07 minutes; The last group: 140.94 ± 28.36 minutes.