Magnification effects on distance estimation during robotic suturing.

We aimed to understand the impact of magnification on distance estimation during robotic suturing. Twenty subjects estimated the lengths of various sutures externally, in plain sight, to validate their ability to measure distances. They then robotically repaired a 3-cm cystotomy, suturing 10 mm above and below the incision and 10 mm on either side of the incision. The bladder was removed and distances measured. A total of 20 surgeons were analyzed: 7 residents, 8 fellows, and 5 staff. Specialties comprised four urologists, eight general gynecologists, two urogynecologists, three gynecologic oncologists, and three reproductive endocrinologists. The mean estimation for external suture length was not significant at 10 mm: mean = 9.6 (±3.2) mm (p = 0.59). When comparing these data sets, the externally visualized 10-mm suture versus the suture-to-suture and the suture-to-incision distances were both significantly different (p = 0.002 and p < 0.001, respectively). The mean distance between each suture was 6.5 (±1.8) mm, which was significantly different from the 10-mm goal (p < 0.001, 95 % confidence interval (CI) [-4.4,-2.6]). The mean distance from the suture to the incision was 4.1 (±1.0) mm, which was also statistically significantly different from the goal (p < 0.001, 95 % CI [-6.3,-5.4]). Surgical experience was negatively associated with suture-to-incision distance (r s = -0.53, p = 0.016). Inter-suture distance was also negatively associated with experience (r s = -0.30, p = 0.22), though not statistically significant. In vivo distances are significantly underestimated during robotic suture placement. Interestingly, the most experienced surgeons had the worst distance estimation from the incision to the suture.