Page 16 - World Journal of Laparoscopic Surgery

Evaluation of Various Port Positions for Minimal Access Cardiovascular and Thoracic Procedures
A thoracoscope attached to a video camera passed through • Port placement to be adjusted according to the specific chest
ports into the chest cavity via 5–10 mm skin incisions where rod anatomy. Most importantly, the skin incision to be placed
lens transmits the signal to see inside the chest on the monitor directly in the middle of the corresponding intercostal space
(Fig. 1). There are two ergonomic principles [baseball diamond to avoid unnecessary pressure on the rib by the instrument
principle (BDP) and triangle target principle (TTP)] for the position during manipulation.
and placement of access ports, which helps in task performance • The optical port is placed at the center so that telescope remains
8,9
and surgeons’ comfort. Three angles are used to perform the task in between the operating instruments, which will act as a type I
in each principle. These manipulation angles are to be evaluated lever with equal length within and outside the thorax.
to find the ideal position. Besides laparoscopic surgery, the BDP is • The manipulation angle between the two operating instruments
1,2
also applied for VATS as a conventional principle. Here the camera would optimally be 60° (elevation angle is 30° and the azimuth
port and the target are placed at the opposing vertical angles of angle is 15°–45°)
the diamond and the other two working instruments are placed • The operating instruments would not face or work against the
perpendicular to that plane at the horizontal angles (Fig. 2). 4,9 telescope as this results in production of the mirror image and
The TTP is relatively a new principle. Here three ports are placed tough task execution with increased error rate.
in a triangle keeping the target lesion at the apex. One side of the • Height of the operating table ought to be adjusted between 64
base becomes the site of the first port for the camera, and the cm and 77 cm higher than the floor level because discomfort
another side becomes the site for the second port for the forceps and operative difficulty are lowest when working instruments
or the endoscopic stapler. The third port is for the forceps to the are positioned at the level of the elbow. 9
target lesion (Fig. 3). 8,10 To explore a prospective experimental • Ergonomically, the monitor image within 25 optimal degrees
animal study was carried out to find out a suitable manipulation below the horizontal plane of the eye offers least neck strain. 11
angle for the port position in TTP using 30°, 60°, and 90° angles • To facilitate easy instrument manipulation and proper
regarding task performance time, error, and comfort of surgeons. visualization, the port to be placed in a triangular fashion.
AIms And objectIves Troubles related to depth perception, vision, and loss of
peripheral visual fields may be reduced by using 10–15×
To evaluate and compare task performance at different port magnification. 12
positions during lung resection, thymectomy, IMA harvesting for • The target organ ought to be 15–20 cm from the optical port.
totally endoscopic coronary artery bypass grafting (TECABG), ASD Generally, the two remaining ports are placed in the same
closure, and esophagectomy through minimal access using the 15–20 cm arc at 5–7 cm on either aspect of the optical port. It
TTP and find out which position for port is better and facilitates makes the instruments to work at a 60–90° angle. If required,
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task performance. additional retracting ports may be placed in the same arc but
ergonomIc PrIncIPle for mInImAl Access more laterally to avoid clashing of instruments. If angle between
target and instrument is too wide or obtuse, manipulation of the
surgery instrument is so tough. That’s why surgeons used to customize
Ergonomics is “the scientific study of individual at work, in terms the port position.
of equipment design, workplace layout, operating environment, • The most effective task efficiency and performance quality are
productivity, safety and training.” The ergonomic principle governs obtained with a perfect manipulation angle between 45° and
the position of ports in minimal access surgery to facilitate higher 60°, which can be achieved by correct placement of ports. The
task performance and comfort to the surgeon. It includes the 90° manipulation angle creates the greatest muscle workload by
following: the deltoid and the trapezius. Manipulation angle starting from

Fig. 1: Basic visual equipment used for minimal access surgery

102 World Journal of Laparoscopic Surgery, Volume 12 Issue 3 (September–December 2019)