Optimal trocar placement for ergonomic intracorporeal sewing and knotting in laparoscopic hiatal surgery

Abstract 

Background

Trocar placement presently is mostly empiric. Our goal was to define simple distances from bony landmarks to locate the optimal ergonomic placement of manipulation trocars for access to the lower esophagus and hiatal orifice, for suture placement, and knotting of the gastric fundus and crura. Hypothesizing that the ideal ergonomic principles of a manipulation angle of 60°, an elevation angle (α_e) of 30° to 60°, and an intracorporeal/extracorporeal length ratio (I/E) of working instruments close to 1:1 are interrelated by simple trigonometric functions, the variations of each of these parameters were calculated in a dependent manner for 2 standard lengths of needle holders: 48.5 cm and 58.5 cm.

Results

Trocar placement can be calculated easily according to simple formulas dependent on the α_e, the distance from the sternoxiphoid junction to the median of the intertrocar span (d) and the vertical distance from the stenoxiphoid junction to the average distance between the apex of the hiatal orifice and the anterior aspect of the esophagus (XH'): when the α_e is 30°: d is XH' √2 and when α_e is 45°, d is XH'/√2. Likewise, when α_e is 30° the intertrocar span (LR) is 2XH', half on either side of the optical axis (d), and when α_e is 45°, LR is XH' √2, XH'/√2 on either side of the optical axis. The most ergonomic solution is to work with an α_e of 40° to 45° by placing the 2 working (manipulation) trocars, between 10 and 14 cm caudad from the sternoxiphoid junction, between 10 and 12 cm on either side of the longitudinal axis corresponding to the optic-target axis. The shorter needle holder works best in this configuration because the I/E ratio will be between .8 and 1. If, however, the surgeon wants to work with an α_e closer to 30°, then the longer needle holder should be used, and the trocars should be placed between 20 and 21 cm from the sternoxiphoid junction, 14.5 to 15 cm on either side of the optical axis. The I/E ratio will vary between 1 and 1.1. When a 1/1 I/E ratio was prioritized, the α_e would be 40° and 32°, for the shorter and longer instruments, respectively. The deeper crural closure requires increasing the α_e by 2° and 3°, respectively. Hyperlordosis, as obtained by placing a cushion under the patient's back, shortens the distances, allowing placement of the trocars closer to the sternoxiphoid junction.

Conclusions

Based on ergonomic principles (manipulation angle, 60°; α_e, 40°–45°; and an I/E ratio of working instruments, close to 1:1), simple trigonometric considerations allow easy calculation of the ideal placement of trocars corresponding to working instruments in hiatal surgery necessary for ergonomic dissection, suturing, and intracorporeal knotting. Ideal trocar placement is dependent only on the vertical depth of the target organ.

Keywords: Trocar placement, Ergonomics, Suture, Knotting, Gastric fundus, Hiatal orifice, Crura, Manipulation angle, Elevation angle, Intracorporeal/extracorporeal length ratio, Trigonometric functions