Seven patients with obesity who met the metabolic surgery criteria set by the Chinese Society for Metabolic & Bariatric Surgery (CSMBS) underwent MicroHand SⅡ robot-assisted sleeve gastrectomy (MⅡSG) from March 2018 to April 2019. All patients suffered from fatty liver with hypertrophic hepatic lobes. Perioperative overall operative time, preoperative setup time, intraoperative blood loss, hospital stays, and perioperative complications were recorded. Anthropometry data, including body weight, body mass index (BMI) and waist circumference (WC) preoperatively and 3 months postoperatively were collected. Percentage excess weight loss (% EWL) was estimated in the following 3 months. % EWL = (weight loss/baseline excess weight) x 100%, where baseline excess weight = baseline weight - ideal weight. The ideal weight is based on a person’s weight at a BMI of 25 kg/m2. All results were expressed as a mean ± standard deviation. The paired-samples T test was used, and the significance level was set at a two-tailed α=0.05. The surgeons had sufficient training to adapt well to the MicroHand SⅡ robot. Written informed consent was obtained from each patient. This study was authorized by the ethics committee of the hospital and registered in the National Institutes of Health website: www.clincaltrials.gov. The registration identifier is NCT02752698.
Overview of the MicroHand SⅡ robot surgical system
The MicroHand SⅡ robot surgical system mainly consists of a surgeon console, a slave robot and a video vehicle (Fig. 1), the structure and appearance of which are distinctly different from those of the da Vinci surgical system. The preloaded cable-driven system and harmonic reducers make it light in weight, compact in structure, and enable a large range of motion. Compared to the MicroHand S, this robot was upgraded successfully in configuration, such as being equipped with an ultrasonic scalpel, a master-slave motion scaling function and an audible alarm function. Both the scaling and alarm functions are integrated into the control panel for quick manual manipulation. Benefitting from using specialized control algorithms, the motion mapping relation can be built up without the help of a built-in image system, which are different from the MicroHand S and da Vinci systems. Therefore, the two-arm MicroHand SⅡ is compatible with conventional endoscopic image systems in hospitals, in which the manipulator used to hold the endoscope is abolished. Thanks to this design, the cost, volume and weight of the MicroHand SⅡ can be further reduced.
The surgeon console allows the surgeon to control multi-DoF instruments by operating master manipulators and foot pedals. The two master manipulators conform to the ergonomic engineering facilitating to filter out hand tremors, relieve hand fatigue and improve precision. Owing to the embedded controller, the motions input by operating master manipulators outside the abdomen can be mapped to the end-effector motions of instruments inside the abdomen cavity exactly. The reproduced motions of the instruments following the master manipulators are activated by grasping the button on the handle. Then, incremental motion is used to reposition the master manipulators during surgery to solve the mutual interference or motion limits of the master manipulators, which is implemented by the clutch mechanism fired by pinching the clamp to disengage the instrument motion from the corresponding motion of the master manipulators. The control panel is used for system initialization and to establish the initial values of certain key parameters prior to surgery. The motion scale between the master and the slave is adjustable among different proportions, such as 3:1, 6:1 and 10:1, by simply clicking the keys on the control panel at any time during the entire procedure (as shown in Fig. 2).
This master-slave motion scaling function improves the accuracy by switching the motion scale during the operation. A 3:1 proportional motion control means the movement of the slave manipulator takes one-third of the master manipulator movement. For example, when dissociating the gastrocolic ligament using the ultrasonic scalpel, the surgeon usually chooses 3:1 to complete resection quickly. When isolating the short gastric vessel, the surgeon can choose 10:1 to refine the operation. The master–slave motion mapping strategies of MicroHand SⅡ are a unique design. The setting can be turned up in fine operations and turned down in extensive operations. This design can improve the safety and speed up the process of the operation and has been well applied in operations.
The audible alarm function is attributed to the sensor equipped in each passive joint, which is to guarantee operation safety. The control system compares the angular positions provided by the sensors and those obtained through the kinematic calculation at each controller time-step. Once the error between them exceeds a certain range, the robot is stopped immediately, and an alarm sounds in the control panel. The surgeon needs clear out the fault first by clicking the button on the control panel and then continue the surgical procedure. The imaging system transmits a stable 3D view in an open-field way (Fig. 3a). Benefitting from the open high-definition 3D view of MicroHand SⅡ, an easier real-time discussion and teaching intraoperative is allowed for, which is inconvenient with a closed image viewer integrated in the console in da Vinci (Fig. 3b). In addition, it is helpful to relieve the surgeon’s neck fatigue without persistently laying the head down against the image viewer for a long time.
The operating arm system is optimized with two movable manipulators installed on the swivel head used to place the instruments (Fig. 4a). The structure of the instrument is designed optimally on the basis of the kinematic analysis together with the ergonomic index. To ensure that the surgical robot can perform the suture motion, which is largely a rotation about the bisector line of the two jaws of the instrument, an end rotational motion needs to be realized. Based on this, a separated roll joint is designed at the distal end of the instrument (Fig. 4b). Eventually, the system allows the manipulator to move with seven DoFs beyond the laparoscopic surgery, technically.
The technical advantages in patient-robot interaction
Patients with obesity have inherent surgical features that greatly increase the operation difficulty. During MⅡSG, the target organ is the stomach in the upper abdominal region; the robot is used to assist in operations. In terms of the LSG surgical requirements, problems related to thick abdominal walls, a mass of visceral fat, deep stomach fundus and limited space to manoeuvre the instrument are always encountered. At the same time, the anterior and posterior diameters of the abdominal cavity are large, and stomach fundus and part of the gastric body in patients with obesity are covered by the plump left liver lobe. However, MicroHand SⅡ has some particular features, especially in patient-robot interaction, to overcome the difficulties in exposure and operation.
It is convenient to locate the slave robot owing to its crossbeam design and flexible swivel head. The route of movement up and down the column of the slave robot is long-range, which is enough to overcome the elevated bed after patients with obesity lay on the bed. The surgeon need not intentionally turn down the bed to adapt to the slave robot. This design can free up space around the patient’s head, which makes general anaesthesia easier during a robotic surgery. It is beneficial to place and settle surgical equipment, including the anaesthetist cabinet, several sterile trays, display monitors, several instrument cupboards, and so on, to satisfy operation room area requirements. However, many pieces of equipment are always stored in every area until needed for surgery. This compact robot does not occupy much room around the patient, keeping the surgeon or assistants close to the patient.
During the whole intervention of the MⅡSG, benefitting from its optimal design, although patients with obesity are large, we can always place the slave robot acceptably without repeated adjustments. The slave robot of the MicroHand SⅡ is well-suited to this situation and can be placed without the need to move and dock the robotic cart several times. It is not affected by the position of the operating bed only meeting the basic placement principle, which is simply that the slave robot is near to the lesion side. The operation site can be completely covered by the workspace of the robot to avoid the need to reposition the robot during the surgery. In the da Vinci surgical system, the slave robot must be placed at a special site near the operation bed. Therefore, the position of the surgical cart is simpler than in the da Vinci system, without repositioning during the entire procedure.
The two manipulators of the slave cart have long arms, which are suited for long-scale adjustments. The kinematic design of the robot arm can fulfil the incision point constraint . The number of joints is set reasonably, and the length proportion of each arm is set appropriately. In the contracted state, each arm is folded together, occupying little space. In the open state, each arm is fully and freely extended to generate a very wide operating field for encircling, avoiding external collisions of the arms. These designs not only meet the space requirements of the abdominal operating area but also meet the requirements of the operating triangle of the working instruments. Therefore, it is easy to position the surgical cart and trocars. The robot can release some of the space around the operating table that may be occupied by the robot arms compared with the da Vinci assisted system. The 450 mm length of the instruments, including robotic graspers, needle holder and ultrasonic scalpel, is longer than that of the da Vinci system, which can fulfil the motion requirements with a maximum moving range of 250 mm for the back and forth motion measured from the incision point.
The MⅡSG port setup is more flexible than the LSG setup in spite of the incision point constraint. The DoFs of the laparoscopic rigid instruments are restricted to four, that is, three rotation motions and one translation motion by passing through fixed small incisions . The mechanism of the robot arm part is composed of three active joints and three passive joints. A fixed point has been used to satisfy the incision point constraint by developing an optimized mechanism in the arm part . The fixed point coincides in position with the location of the skin incision leading to positioning algorithms with roll angle and pitch angle, as shown in Fig. 5.
Surgical technique: MⅡSG
After general endotracheal anaesthesia was performed successfully, the patient was placed in the supine position with his or her legs by the side. After the abdomen was sterilely prepared and draped and a foley catheter was inserted, pneumoperitoneum was created with a Veress needle at a point 1 cm superior to the umbilical fossa up to a pressure of 14 mmHg. Then, a 12 mm trocar was inserted for placing a 45° and 12-mm 3D laparoscope as the camera-holder port (A0). The distance between A0 and the umbilicus varied to achieve the proper angle of best visualization. The two ports for the robotic instrument arms (R1 and R2) were set up next. The distances for instrument port placement were measured after insufflation with individualized design, and at least a fist length (10 cm) was maintained between all ports. R1 (8-mm MicroHand cannula) was established at the left midclavicular line superior to the A0 level. R2 (8-mm MicroHand cannula) was placed inside the right midclavicular line superior to the R1 level, with care taken to ensure that the route of the instrument was under the margin of the left liver. In particular, R1 was replaced by a 12-mm trocar as the camera-holder port during the stapling, provisionally. A0 was used as the stapler port, accordingly. In addition, another 5-mm port was placed at the anterior axillary line in the left hypochondrium as an assistant port (A1), which was used to retract the left lobe of the liver, assist stapling and so on.
The patient was placed in the steep reverse Trendelenburg position. The slave robot was brought from one of the available sites on the left side of the patient, and docking was performed in a short time. The camera-holder stood between the patient’s legs. The assistant surgeon was on the left of the operating table. Although the fundus of the stomach was very close to the spine, which is far from the port site, especially for patients with obesity, the range of the instruments was sufficient to reach the fundus field and His angle to isolate tissue and to finish the separation of the fundus.
The two main steps of sleeve gastrectomy include the complete dissection and subsequent resection of the greater curvature and gastric fundus. Safe exposure and mobilization of the fundus are regarded especially as the crucial procedure of a sleeve gastrectomy. Gastrolysis was performed along the greater curvature of the stomach from the prepyloric region to the His angle using a MicroHand ultrasonic scalpel. The short gastric vessels from the gastrosplenic ligament and posterior gastric adhesions with the pancreas were divided. The left crus was completely defined so that the fundus was adequately mobilized. Instead of a bougie, a gastroscope was placed through the pylorus into the first part of the duodenum and was kept in place to guide the sleeve formation. The console surgeon applied traction on the stomach so that it was in the right orientation. Continuous stapling started 5 cm from the pylorus towards the His angle using a linear stapler through the A0 port to resect the stomach by a patient-side surgeon with adequate training in LSG skills. Instead, R1 was replaced by a 12-mm trocar with the laparoscope inserted. After gastric resection, gastroscopy with saline solution immersion was performed in all cases to rule out any leak, bleed, or obstruction. Finally, the resected stomach specimen was removed through the accessory port, and one drain was left in the peritoneal cavity. The port placement, operation room layout and detailed reality images of the robotic operating procedure are shown in Fig. 6.