Single-incision laparoscopic surgery increases the risk of unintentional thermal injury from the monopolar "Bovie" instrument in comparison with traditional laparoscopy.

Background: Single-incision laparoscopic surgery (SILS) places multiple instruments in close, parallel proximity, an orientation that may have implications in the production of stray current from the monopolar "Bovie" instrument. The purpose of this study was to compare the energy transferred during SILS compared to traditional four-port laparoscopic surgery (TRD).

Method: In a laparoscopic simulator, instruments were inserted via SILS or TRD setup. The monopolar generator delivered energy to a laparoscopic L-hook instrument for 5-s activations on 30-Watts coag mode. The primary outcome (stray current) was quantified by measuring the heat of liver tissue held adjacent to the non-electrically active 10-mm telescope tip and Maryland grasper in both the SILS and TRD setups. To control for the potential confounder of stray energy coupling via wires outside the surgical field, the camera cord and active electrode wires were oriented parallel or completely separated.

Results: SILS and TRD setups create similar amounts of stray current as measured by increased tissue temperature at the non-electrically active telescope tip (41 ± 12 vs. 39 ± 10 °C; p = 0.71). Stray current was greater in SILS compared to TRD at the tip of the non-electrically active Maryland forceps (38 ± 9 vs. 20 ± 10 °C; p < 0.01). Separation of the active electrode and camera cords did not change the amount of stray energy in the SILS orientation for either telescope (39 ± 10 °C bundled vs. 36 ± 10 °C separated; p = 0.40) or grasper (38 ± 9 °C bundled vs. 34 ± 11 °C separated; p = 0.19) but did in the TRD orientation (41 ± 12 bundled vs. 24 ± 10 separated; p < 0.01). When SILS was compared to TRD with the cords separated, SILS increased stray energy at both the telescope tip and grasper tip (36 ± 10 vs. 24 ± 10 °C; p < 0.01 and 34 ± 11 vs. 17 ± 8 °C; p < 0.01).

Conclusion: SILS increases stray energy transfer nearly twice as much as TRD with the use of the monopolar instrument. Strategies to mitigate the amount of stray energy in the TRD setup such as separation of the active electrode and camera cords are not effective in the SILS setup. These practical findings should enhance surgeons using the SILS approach of increased stray energy that could result in injury.