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 degrees, an elevation angle
(alpha(e)) of 30 degrees to 60 degrees, and an
intracorporeal/extracorporeal length ratio (TIE) 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 alpha(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 alpha(e) is 30 degrees: d is XH’ root 2 and when
alpha(e) is 45 degrees, d is XH’/root 2. Likewise, when alpha(e) is 30
degrees the intertrocar span (LR) is 2XH’, half on either side of the
optical axis (d), and when alpha(e) is 45 degrees, LR is XH’ root 2,
XH’/root 2 on either side of the optical axis. The most ergonomic
solution is to work with an alpha(e) of 40 degrees to 45 degrees 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 alpha(e) closer to 30 degrees, 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 alpha(e) would be 40 degrees and 32
degrees, for the shorter and longer instruments, respectively. The
deeper crural closure requires increasing the alpha(e) by 2 degrees and
3 degrees, 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
degrees; alpha(e), 40 degrees-45 degrees; 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.
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