Innovations in Hepatopancreatobiliary Surgery: A Review of LOTUS-BOWA Liver Blade and AEON Endovascular Stapler Open Access

Hepatopancreatobiliary (HPB) has generally been regarded as one of the more complex specialties in general surgery. It is very organ specific and requires specialized equipment for parenchymal transection, which, to date, have been described and used to a high level. The main caveats with the organs are that the liver has a tendency to bleed and also suffers from biliary duct damage with consequent leaks, and the pancreas suffers from pancreatic fistula formation, which can sometimes be a hindrance to recovery with serious adverse events occurring as a result, including mortality. When potential new instruments are introduced into a surgeon’s armamentarium, it becomes important for an HPB surgeon to see if the technology can be adaptable in the liver and pancreatic parenchymal tissue and how best it can be used to improve patient outcomes. In the past, there has been no consensus reached in terms of what is the preferred transection “tool” to be recommended, especially in liver surgery, with an emphasis placed on a surgeon knowing and understanding the technology of any instrument they use, as well as combining it with their experience.^[1] This review article discusses two innovative instruments, the LOTUS-Bowa liver blade (BOWA-electronic GmbH, Gomaringen, Germany) and the AEON endovascular stapler (Lexington Medical, Boston, MA, USA).

A literature search was undertaken in PubMed using the “MESH” browser terms “liver and pancreas resection techniques,” “ultrasonic dissection,” and “endovascular stapler” from January 2010 to June 2024, with a further emphasis on level I–III evidence only.

Ultrasonic devices have been used in surgery, particularly laparoscopic surgery, for the last two to three decades.^[1] They rely on ultrasonic waves to form heat, which simultaneously cuts and cauterizes tissue. This enhanced dual action provides a more hemostatic dissection plane. It enables surgery to be undertaken more swiftly as opposed to the traditional cut-and-tie method, which would be arduous and technically more demanding, especially in a laparoscopic setting.^[2,3] The technology uses ultrasonic waves at 55.55 kHz, which create enough heat by applying pressure to seal tissue with a denatured protein coagulum and ultrasonic vibration to denature hydrogen bonds, which enable vessel coagulation. Ultrasonic dissection used in this way has been shown to be more precise in dissection, create reliable hemostasis, less lateral thermal spread and charring, and a swifter operating time.^[3] One large review showed level I evidence where the harmonic scalpel was used in various trials across different specialties, and it clearly demonstrated improved outcomes at every level.^[4] These studies examined the Harmonic device made by Ethicon (Harmonic Devices; Ethicon Inc., Cincinnati, OH, USA). This device has also been shown to have a quicker operating time with no detrimental effect on hemostasis in a comparative study with an advanced bipolar device called LigaSure (Valleylab, Boulder, CO, USA).^[5]

In HPB surgery, the Kelly-clamp method is still one of the most widely used techniques for liver resection. However, ultrasonic dissection using the Cavitron Ultrasonic Surgical Aspirator (CUSA) has become the standard technique of liver resection in most operations, with one large comparative study favoring Ligasure, although the crush-clamp method still showed good outcomes, with experience in the use of any instrument remaining a key reason for its use.^[6] The harmonic scalpel is not considered a standard technique for parenchymal liver transection but has been described as a possible method; however, this has not been transcribed into a popular adopted method by most HPB surgeons.^[7,8]

Of note, larger comparative reviews examining CUSA (Tyco Healthcare, Mansfield, MA, USA), clamp-crush, radiofrequency dissecting sealer, and hydrojet demonstrated showed that, although newer technologies were proving beneficial in terms of no increase in blood loss, the tried and tested clamp-crush technique was still an excellent method of liver transection.^[6,9]

The LOTUS device is a powerful torsional ultrasonic scalpel that simultaneously seals, coagulates, and cuts tissue like other ultrasonic devices, as described above. Most other ultrasonic dissectors on the market rely on a longitudinal modality of energy delivery. The LOTUS device operates between a frequency window of 35.4–36.6 kHz and uses a torsional modality of energy instead, which gives it an enhanced safety aspect to the device. The LOTUS system’s strengths lie in a reduced stray energy dissipation at the tip of the device, especially when compared with conventional longitudinal instruments. This allows the vessels to be sealed quickly and reliably with a smaller tissue thermal spread footprint. LOTUS makes two instruments used for ultrasonic dissection, a dissecting shear, and a liver resector. Both use the same modality of torsional energy to coagulate, seal, and cut tissue; the fundamental difference between the two models is the profile of the distal tip of the waveguide (Fig. 1).

The LOTUS liver resector has been specifically designed with a conical shape for parenchymal tissue. It has a larger, flat contact surface area, so the distal tip of the liver resector is designed to create a more robust hemostatic effect.

The device has both a high and a low setting and an ultra-low setting. For the liver parenchyma, the low setting is preferred in terms of use. The device can coagulate blood vessels up to 4 mm in diameter with good hemostasis and safety. It can also seal small biliary radicals that are noted at the time of surgery.^[10] For larger glissonian pedicles, other transectional and sealing methods are required, such as an endovascular stapler, as we will discuss below.

The LOTUS ultrasonic energy device consists of the economically reusable ultrasound transducer and the single-use handpiece (Fig. 2). The reusable transducer is made from medical-grade titanium. It has a lifetime of 250 minutes of activation time or approximately 50 cases.

The handpiece is designed (Fig. 3) with a circular control anteriorly to allow rotation of the end blade. In addition, the black grip handle is the main driving mechanism, which controls the ultrasonic power with the surgeon’s grip power, which can be either soft or hard. The grip handle also has a small white button, which will change the setting to low or high, depending on the speed the surgeon wishes to use.

This is the first and only ultrasonic instrument that has specifically been designed for liver parenchymal transection. It has shown great use and versatility with no adverse effects in terms of any increase in bleeding, return to theatre, increased length of stay, and/or bile leakage.^[10] Another study compared both LOTUS and Harmonic for liver transectional surgery and found no difference between the two in terms of bleeding and bile leaks, which is the only comparative study to date but was not prospectively carried out.^[11]

The LOTUS energy device can be used like a CUSA. The bottom blade can dissect blood vessels quite easily, especially as the trajectory of the ultrasonic waves is in a longitudinal and rotational direction. This dissection will then allow blood vessels to be localized and skeletonized; those that are at least 4 mm in diameter or below can be cauterized very easily with the device.

In the study described where the use of the LOTUS energy device compared with open resection,^[11] all of the other approaches that are employed to try and prevent blood loss were utilized in both open and laparoscopic surgery with the use of a low central venous pressure, pringle maneuver, and hypoventilation.^[12] Laparoscopic surgery just used the LOTUS energy and open surgery used CUSA. The CUSA works by combining ultrasonic energy with aspiration to divide the liver parenchyma and thus skeletonize small parenchymal vessels and biliary structures greater than 2 mm, which are then divided according to a surgeon’s preference.^[13] The tip of the CUSA is particularly adept at dissecting away liver tissue to delineate blood vessels as well as major pedicles (Supplemental Fig. S1, available online). The tip of the CUSA cauterizes smaller blood vessels; this is analogous to how the bottom blade of the LOTUS energy device shears can also be used. The LOTUS shears are, therefore, kept open, and when a blood vessel is skeletonized, it can be crushed with the LOTUS shears and divided using its ultrasonic energy. Success has been shown subjectively to completely ligate blood vessels up to 4 mm and sometimes 5–6 mm in diameter, including the hepatocaval ligament (Fig. S2). Care and experience are required to complete this task with good hemostasis. An alternative device, such as an endovascular stapler, is advised for any larger blood vessels to safely transect the vessel and secure hemostasis.

The LOTUS liver blade has shown versatility, especially regarding HPB resections. It can be used like a CUSA to transect the liver parenchyma safely and effectively without causing heat damage to the many vascular structures that are present within the liver parenchyma. Hemostatic control can also be achieved by closing the blades over small blood vessels up to 5 mm in diameter. For larger blood vessels, the surgeon’s preferred technique should be used, whether it be using a stapler or titanium clips. Care should also be taken to avoid overheating of the lower blade; however, as a safety precaution and to reduce the build-up of heat, the LOTUS generator will automatically time out after 25 seconds. The generator will alert the user with a five-beep audio tone and display the feedback symbols of a clock and information triangle (Fig. S3). To resolve this issue, the user must release the activation button.

The LOTUS transducer has a lifetime of 250 minutes of activation time. The generator will notify the user when the transducer reaches 98% of its lifetime by displaying a transducer symbol, a clock, an information triangle, and a message saying final surgery (Fig. S4). The transducer can be used for the remainder of the case so long as it is not unplugged from the generator and/or the generator is not switched off.

Another important troubleshooting message the LOTUS generator will display alerts the user when the transducer can no longer be used. This is displayed on the generator with a transducer symbol, a clock, a red information triangle, and a red “Do not use” message (Fig. S5). This message will be displayed if the transducer has passed its lifetime or has previously been damaged and locked by the generator. The value of the troubleshooting mechanisms is important as the LOTUS blade can heat up, and this will deactivate the device, with a short “cooling-off” period allowing safe dissection to continue. In this study, there was no real negative outcome of using the device, such as a change in the instrumentation of the transducer.^[10]

In summary, the LOTUS transducer is effective in HPB surgery, particularly liver parenchymal transection. Comparative studies with other instruments used in a similar setting have been favorable and shown no inferiority with no increase in the need for a return to theatre for bleeding, blood transfusions, and bile leaks.^[10] Subjectively, it has been shown to be slower than CUSA, but its use in laparoscopic surgery has been shown to be relatively free of bleeding, and this was probably related to the routine use of the pringle maneuver and the pneumoperitoneum.^[10] It is very rare to find an ultrasonic device designed specifically for liver parenchymal transection, and this device has shown great promise with the ability to safely dissect away parenchymal tissue, hemostatically ligate sub-centimeter blood vessels and structures, such as the hepatocaval ligament.

Further data has since been collated regarding the LOTUS liver blade, showing that its effectiveness in liver transection remains, but with a learning curve establishing quicker and comparable transection times compared with open surgery, where previously the transection time was significantly greater.^[12] However, as this experience on the LOTUS liver blade grew, as demonstrated in the revised long-term data of 116 patients from 2020 to 2023, the reliance on pringle remained greater with the minimal access approach with a sustained significant increase (48.5 vs 33 minutes; p = 0.010). However, importantly, a significantly reduced hospital stay (mean 7.8 vs 14.7 days; p = 0.025) and reduced blood transfusion requirements (0 vs 4 units; p = 0.035).^[14] These long results most likely preserve the author’s awareness of the greater risk to the patient with any extreme or uncontrollable bleeding when using minimal access as compared with open approaches.^[14]

The liver is a solid organ, which, unlike the pancreas, does have a capsule, but when it is transected to remove a tumor, its capsule is breached, exposing its parenchyma. The transected liver parenchyma is referred to as the raw surface, where both blood vessels and bile ducts are exposed. Therefore, it is essential that safe and effective dissection of the vessels and the liver parenchyma, with control of intraoperative bleeding, are addressed when performing liver resection.^[15] Stapling devices are used to safely divide hepatic and portal veins, as well as transect liver parenchyma in both open and laparoscopic liver resection. Surgeons use staplers to make manipulation simpler, faster, and safer.^[16] Staplers can also be used effectively to reduce blood loss in hepatic surgery by controlling inflow and outflow vessels,^[17] which has a positive net effect of reducing complications.^[18] Examining all aspects of HPB surgery, the authors’ recent study also examined the stapler’s effective use on pancreatic parenchymal transection, particularly in distal or lateral pancreatectomy, where there was a statistically significant reduction in pancreatic leak rates using the newly introduced AEON stapler.^[19]

The AEON surgical stapler, like other surgical staplers on the market, is used to simultaneously cut and staple tissue when resecting, transecting, or even when creating an anastomosis. This innovative product is used across surgical specialties, including general, abdominal, gynecologic, pediatric, thoracic, bariatric, colorectal, urological, and HPB surgery. The instrument may be employed in both open and minimally invasive laparoscopic surgery, like most other staplers^[15] (Fig. 4).

This article concentrates on innovations in surgery that have aided HPB surgery in particular. Therefore, the impetus for the development of the AEON endostapler was the observation by the manufacturer that innovation in the surgical stapler category, once a leader in new surgery technology, had stalled despite an accumulation of surgeons’ unmet needs. The manufacturer set about to release a new endostapler that combined new proprietary innovations while also drawing the best design features from existing devices. Furthermore, the manufacturer ensured that there was a robust collaborative approach used to develop the AEON stapler by closely working with surgeons and formulating new improvements.

So, what makes this stapler innovative? The first is the handle, which is designed with improved ergonomics so the surgeon can comfortably hold the stapler and feel the tissue. The handle comes in the following three differing sizes: 60, 160, and 260 mm, which are referred to as short, medium, and long handles, respectively. All the shafts have identical diameters, so they will fit comfortably into a 12-mm trocar port. Practically, the long and medium handles are more commonly used in laparoscopic surgery, while the short handle is preferred for open-abdominal surgery, where the reduced shaft length allows the surgeon to have better control during stapling.

The second component is the reload cartridges, which contain single-use titanium staples and blades and are designed for the creation of the staple line. The reloads are available in 30 different configurations, thereby increasing the diverse and unique clinical scenarios in which a surgical stapler can be used. The factors contributing to the need for different reload configurations include varying tissue and vascular thickness, tissue health, tissue type, surgeon visibility limitations, proximity of target transection area to delicate structures, and size of target stapling area.

The AEON reloads are available in five colors. Each color denotes a different size for the staples deployed from the reload. The shortest staple height is in the gray reload, which is most commonly used for vascular transection. The tallest staple height is in the black reload, which is used for the thickest tissue, such as the stomach.

Each cartridge color, with recommended use in HPB surgery, is described below:

• Black: designed for thick tissue and is most applicable for gastrointestinal (pylorus) tissue or otherwise fibrotic or dense tissue

• Purple: gastrointestinal and some pancreas transections

• Orange: medium thickness gastrointestinal tissue and most pancreas transections

• White: thin tissue, vascular use

• Gray: vascular use, especially smaller-diameter blood vessels

Finally, reloads create an increase in the surgeon’s armamentarium with their availability in three lengths and are denoted by the staple-line length. These lengths are 60, 45, and 30 mm. Reload length selection is usually a function of the target area size for dissection. A portal vein transection will likely warrant a 30-mm reload. By contrast, an antrum resection requires multiple 60-mm cartridges, with a 45-mm reload most appropriate for a duodenojejunostomy.

The third is that all cartridges have three differing tips or anvils for surgeon preference in various stages of an operation, as discussed below.

The anvil is the metal plate sitting opposite the colored staple cartridge. When staples are deployed from the cartridge and pierce the target tissue, the staples come into contact with the anvil, where precisely formed metal drives the staples to curve and form a “B” shape.

AEON staple formation is identical across anvil types. The products are differentiated in anvil tip geometry with the following three anvil tips available: regular, short, and curved (Fig. 5).

1. Regular: For both hepatic parenchymal and major vessel transection.

2. Short: Preferential for mid-parenchymal transection, where the deeper tissue, especially in the liver, is not clearly identifiable, thereby potentially avoiding middle hepatic vein tributaries. The shorter “bites” are also ideal for mesentery dissection, such as dissecting mesentery, especially when taking down the duodenojejunal flexure in Whipple pancreaticoduodenectomy.

3. Curved tip: Ideal for encircling hepatic and portal veins. It can also be used in pancreatic surgery to clearly dissect out and isolate the splenic artery in lateral pancreatectomy surgery. It may also be beneficial in pancreatic transectional surgery, as the curve will ensure the upper border of the pancreas is within the transactional pancreatic tissue and so reduce the likelihood of inadvertently damaging the hepatic artery and/or the coeliac trunk.

The smooth articulation of the handle, the superior staple heights and lines, and the multi-gears are all features of the AEON stapler that are described by the manufacturer as S3 engineering (Fig. 6).

The authors’ own experience of using the innovative S3 engineering technology demonstrated a markedly reduced pancreatic leak rate from using another stapler and changing over to AEON, from 65–20% (p = 0.018) by using the orange stapler for the pancreatic transection in lateral pancreatectomy^[19] (Figs. S6–S8). Subjectively, the smoother ratchet was experienced by all the surgeons with the sudden “clicking” to the preferred angle, as noted with the Endo-GIA not experienced.

Having discussed the core product design, AEON innovations may now be described, contributing to its excellent functionality as a vascular and endoscopic stapler.

When considering the gear system, firing in a slow and controlled manner prevents deploying a staple line hastily, which could result in detrimental movement of the staple when clamped down on the tissue. Such sudden movements can potentially cause tissue tearing or bleeding and may also subversively contribute to staple formation and cut-line quality.

The importance of slow and controlled firing leads to the third technical attribute of S3 Engineering, as described above, the multi-speed gear (see appendix; multi-speed gear system). When trying a new endovascular stapler, it is important for a surgeon to feel safe that the instrument will not lead to any increase in complications, especially bleeding, which was demonstrated in the pancreatic study.^[19]

When a surgeon chooses to use new equipment, above all, they need to ensure that it is safe to use. Patient safety compromise is something that would not be tolerated at any level as the worst possible result would be not only a surgeon’s satisfaction but a poor patient outcome. All surgical equipment used in the operating theatre has already undergone vigorous testing before being allowed into the market, whether they have local national approval or the Food and Drug Administration, which is required for medical devices in the United States. So, knowing that the equipment is safe, there remains great emphasis on determining whether the design and functionality will be appropriate for use in a specific tissue or organ. In terms of HPB surgery, liver bleeding and bile leaks are the main parameters that a surgeon uses to decide whether an instrument is suitable, with pancreatic surgery also relying on leakage or pancreatic fluid from the parenchyma and bleeding as important markers of good functionality. Both complications can present with major problems, including a much higher morbidity and an unexpected rise in mortality.

Weighing all of the options is important for surgeons; however, there’s also a cost implication with both of these instruments, which provides safe surgery with excellent patient outcomes at no increased cost. The average cost per liver resection with the use of CUSA is estimated at $482 and for LOTUS at $395, making a potential savings of $87 per case.

Further studies will need to examine both instruments in direct comparison with other similarly designed instruments and preferably in a randomized setting, although matched propensity studies have been undertaken already.^[3] One such comparative study, although with small numbers, looked at bleeding rates after sleeve gastrectomy using the AEON stapler as opposed to the Echelon Flex and found a reduction in bleeding with the former, but further numbers are ideally required for this study to immediately instigate a change in practice.^[20] Notwithstanding a larger study for the same operation, which also demonstrated and provided more robust evidence in a randomized setting, that the use of AEON endovascular stapler reduced bleeding along the staple line in sleeve gastrectomy compared with the popularly used stapling device made by Medtronic Endo-GIA.^[21]

Recent innovations in HPB cancer surgery have introduced groundbreaking techniques aimed at improving precision, safety, and patient outcomes.^[22] Minimally invasive and robotic-assisted surgeries are becoming more feasible with advancements that address technical challenges, such as hemorrhage and CO₂ embolism.^[22] Irreversible electroporation, a nonthermal ablation method, is gaining traction for treating tumors near vital structures, particularly in locally advanced pancreatic and liver cancers.^[23] Radiation lobectomy, which uses radioactive microspheres to increase the future liver remnant volume, has shown promise in converting unresectable liver tumors into resectable cases.^[24] Technologies like dynamic optical contrast imaging are enhancing tumor margin delineation, potentially increasing resection accuracy. Integrating artificial intelligence, 3D imaging, and advanced planning tools further supports surgeons in achieving better outcomes while reducing complications.^[25] These advancements mark a significant leap forward in the surgical management of HPB cancers.

Eventually, it is expected that using both instruments’ innovative technology on a robotic platform will be very useful, especially with the liver blade and its specialized conical shape and the AEON stapler with its B-shaped uniform staple line and S3 engineering.

Innovation should always be practiced with all types of surgery. In what is considered a high-risk surgery, such as HPB, care must also be emphasized for patient safety, specifically looking at bile leaks with liver transection and pancreatic fistulas from pancreatic parenchymal dissection and bleeding. Both instruments have demonstrated excellent outcomes with no adverse increase in these above complications and are recommended for use in HPB, with experience demonstrating a distinct advantage.