What is the difference between LigaSure and Harmonic?

During minimally invasive laparoscopic surgical procedures, particularly in thyroidectomy, the need to cut, ligate and seal an artery or a tissue commonly arises in order to stop the blood supply to a certain area and maintain homeostasis. For this purpose, multiple vessel or tissue-sealing devices are used. Two of these important devices include the LigaSure vessel sealing system and the Harmonic scalpel.

LigaSure, abbreviated as LVSS, is a single-use electrothermal bipolar vessel sealing system employed for vascular fusion during various medical procedures. It provides a voltage of 180V to the target tissue resulting in a temperature elevation of up to 1000°C. This high temperature renders the tissue collagen and elastin to melt thus denaturing the hydrogen cross-linking. As a result, fusion at the target tissue occurs with a diameter of 7 mm along with higher tensile strength. Its working time falls between 2 to 4 seconds.

The jaw of the LigaSure vessel sealing system (LVSS)

On the other hand, a Harmonic scalpel (HS), unlike LVSS, is an ultrasonic vessel cutting and cauterization system which provides power to the target tissue at a high frequency. Its frequency range can be set from as low as 15,000, 25,000, 35,000, and 45,000 to the maximum up to 55.5 kHz or 55,500 vibrations/second. It generates mechanical energy from the ultrasonic energy which denatures the coagulum protein at the target site resulting in the fusion of vascular tissue. Dissection conducted using ultrasonic technology is called ‘Ultracision’. Its ability to cut through tissue while coagulating renders it dominant in comparison to the LigaSure vessel sealing system. The technique can be used in place of laser therapy as well as electrosurgery.

A Harmonic scalpel (HS) with its two jaws visible i.e. active (vibrating) and inactive (straight) jaws

Difference between LigaSure vessel sealing system and Harmonic scalpel

LigaSure system works by the unipolar or bipolar electric current provided to it which it further uses to cut and seal the body tissues. On the contrary, the Harmonic scalpel does not use electric current. Rather, it works by producing ultrasonic vibrations at the target site resulting in the cutting action. Both the LigaSure vessel sealing system and the Harmonic scalpel can be employed in one surgical procedure at different steps to fulfill multiple purposes. For instance, during lung surgery, HS can be used to make an incision while LVVS can be employed to fuse the tissue.

LVSS and HS being used in a lung procedure: (a) Harmonic scalpel is being employed to cut the lung parenchyma, (b) visceral surface is visibly cut, and (c) LigaSure vessel sealing system is being used to fuse the area

Comparison of LigaSure vessel sealing system and Harmonic scalpel

Although both devices find application in similar medical procedures, there exist some differences in their working principles, burst pressures, duration of operation as well as cost. Therefore, LVSS and HS can be compared in terms of the following parameters:

Parameters	LigaSure vessel sealing system (LVSS)	Harmonic scalpel (HS)
Working principle	Electrosurgery	Ultrasonic vibrations
Visibility	Impaired visibility due to smoke production	Impaired visibility due to mist production
Operation time (min)	Slow surgery (187.6 min)	Slower surgery (184.2 min)
Burst pressure (mm Hg)	Moderate mean burst pressure (591 to 836)	Lowest mean burst pressure (1078 to 1314)
Thermal spread	2 mm lateral thermal spread	Less than 1 mm thermal spread
Cost of the procedure (i.e. thyroidectomy)	$2,300 approx.	$1,600 approx.
Post-operative calcium levels (mg/dl)	8.2	8.4

Applications of LigaSure vessel sealing system and Harmonic scalpel

Some of the following conditions require the employment of vessel sealing systems:

• Surgery of the vascular system i.e. Angioplasty
• Removal of the uterus i.e. Hysterectomy
• Liver resection surgery
• Colorectal procedures
• Thyroid removal surgery i.e. Thyroidectomy
• Endocrine surgeries
• Esophageal cancer surgeries
• Lymphatic vessel surgery i.e. Lymphaticovenous anastomosis
• Antireflux surgery
• Surgical removal of blood clots from pulmonary vasculature i.e. Pulmonary thromboendarterectomy (PTE)
• Surgical treatment of piles
• Thyroid lobes removal i.e. Thyroid lobectomy
• Uterine fibroids removal i.e. Myomectomy

Advantages of LigaSure vessel sealing system and Harmonic scalpel

Both vessel fusion systems provide the following advantages:

• Both the LVSS and HS techniques are safe to use.
• Both the LVSS and HS methods are time efficient.
• Both devices depict a thermal spread that is minimum.
• Dissection is precise and accurate.
• Minimum to zero tissue sticking with the device’s jaws is observed.
• Instrument exchanges are not frequent.
• Post-operative complications are fewer.
• Blood loss during and after the procedure is insignificant.
• Skin incision length is minimal.

Side effects of LigaSure vessel sealing system and Harmonic scalpel

The following issues may be associated with the use of LigaSure vessel sealing systems and Harmonic scalpels:

• Smoke formation during LVSS use and mist formation during HS use can reduce visibility during the medical procedure.
• The current provided by these devices can highly elevate the temperature of the target tissue which may result in burns.
• Contact of the devices with nearby tissues can cause collateral damage.
• Undercooking of the tissue may occur i.e. at lower than the required voltage, the tissue cross-linking may not occur up to the necessary level resulting in the use of scissors to properly disjoint the tissue.
• Mild hypocalcemia i.e. reduced calcium level in the tissue can occur.
• Post-operative mild blood loss near the target area can also occur in some cases.

Conclusion

Minimally invasive surgeries are the preference of medical professionals due to their ease of conduction, lesser risk due to lesser blood flow, fewer post-operative complications as well as reduced overall cost. LigaSure vessel sealing system and Harmonic scalpel are two efficient medical devices that can be employed to achieve the purpose of vessel or tissue fusion during surgeries. Their safety, effectiveness, and efficiency have rendered them superior to other means of tissue sealing.