Robotic Surgery Assisted by the ZEUS System

Masatoshi Eto and Seiji Naito

Summary. Urology has continuously embraced novel technologies, such as shockwave lithotripsy, lasers, and laparoscopy, that reduce patient morbidity yet maintain an excellent standard of care. To potentially increase the clinical applicability of laparoscopy, robots that enhance operative performance have recently been introduced for a variety of laparoscopic procedures, such as laparoscopic radical prostatectomy, pyeloplasty, and nephrectomy. Although the introduction of robotics has generated excitement, its benefits in large series of patients remain largely unknown. In this review, we mainly focus on one of the available robotic systems, the ZEUS system, and describe its features, including its advantages and limitations. We also review the emerging clinical applications of the ZEUS robotic system, including our recent cases of laparoscopic radical prostatectomy assisted by ZEUS, and the future potential of robotics in urology.

Keywords. Robotic surgery, ZEUS, Laparoscopy, Urology, Radical prostatectomy

Introduction

In the last 10 years, laparoscopy has revolutionized urology. However, many laparoscopic techniques (e.g., intracorporeal suturing) remain more difficult to perform than the corresponding tasks in open surgery. Furthermore, conventional laparoscopy imposes limitations on maneuverability (secondary to trocar positioning), vision (two-dimensional on flat screen), dexterity (secondary to long, awkward instruments), and tactile sensation when compared with open surgery. Therefore, robots that enhance operative performance may increase the applicability and precision of laparoscopy, yet decrease the learning curve of these minimally invasive tasks.

Department of Urology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan

Robots are increasingly utilized in urology, in part because of their favorable performance characteristics. Robots perform tasks quickly with excellent precision. Robots do not fatigue, regardless of time or environment, and can be more cost-effective than humans. The function of robots, however, remains heavily influenced by human factors. Indeed, industrial and medical robots function only as well as the software or operators controlling the devices. Recently, two performance-enhancing robots were introduced to increase the clinical applicability of laparoscopy [1-4]. One is the "da Vinci" system (Intuitive Surgical, Mountain View, CA, USA), and the other is the "ZEUS" system (Computer Motion, Goleta, CA, USA). In this manuscriptchapter, we focus on the ZEUS system and review the advantages and limitations of ZEUS and emerging clinical applications of ZEUS, including our recent cases of laparoscopic radical prostatectomy assisted by ZEUS.

Robotic System and Technical Factors

The ZEUS robot is a master-slave system consisting of two physically separated subsystems named "surgeon-side" and "patient-side" (Fig. 1a, b). The surgeon's subsystem has a console that takes the surgeon's input, and the patient's subsystem includes two robotic arms and the automated endoscope system for optimal positioning (AESOP). AESOP is designed to manipulate a laparoscope. The Food and Drug Administration (FDA) approved the use of AESOP in 1994. AESOP uses one mechanical arm with six degrees of freedom (DOFs) that is mounted to the operating table (Fig. 2a, b) [5-8]. AESOP is actively controlled by foot, hand, or voice commands. For increased safety, the laparoscope coupling mechanism disengages if more than 5 pounds of force is applied to the robotic arm during movement.

AESOP has been used for many laparoscopic procedures in multiple sub-specialties. At Johns Hopkins University, Kavoussi et al. evaluated AESOP for urologic procedures, including ureterolysis, lymph node dissection, nephrec-tomy, and pyeloplasty [6]. The group found that AESOP maintained a steady image throughout surgery and eliminated the need for surgical assistants [6]. Kavoussi et al. performed a blinded study comparing laparoscopic manipulation by humans versus AESOP. With AESOP, the laparoscopic images were steadier and instrument collisions were decreased [7].

The main advantages of AESOP-assisted procedures are the excellent image quality and the steadiness of the operative view. With AESOP, surgeons depend less on human assistants while performing laparoscopy (Fig. 2c, d). AESOP has also made telementoring possible with laparoscopy [6, 9]. In this manner, an operator at a remote site (located even many kilometers away) can control the endoscope with AESOP for instructional purposes. For instance, researchers at the University of Innsbruck and Johns Hopkins University have previously reported the feasibility of laparoscopic telementoring for a procedure performed in Innsbruck, Austria, and telementored from Baltimore, Maryland, USA [9].

Zeus Robotic Surgery
Fig. 1. ZEUS robotic systems. a The surgeon's robotic console. b Robotic arms on the patient's side. c The ergonomic handles of the recent version of ZEUS. d The new three-dimensional imaging system

AESOP is acquired with a relatively minimal capital investment, and the additional operative costs are minimal.

As with AESOP, the robotic arms are directly mounted to the operating table and are positioned through conventional trocars. A variety of surgical instruments can be connected to the robotic arms, so that the surgeon can activate the graspers, scissors, hook, and other instruments simply by manipulating the handles at the remote console. Standard ZEUS instruments have four DOFs, but newer articulating Microwrist instruments have five DOFs. All instruments are reusable and incorporate a durable pull-rod design. The surgeon sits in a comfortable chair in front of the video monitor, and the computer interface can eliminate the surgeon's resting tremor and be set to downscale the surgeon's hand movements over a range of 2:1 to 10:1. The recent version of ZEUS uses more ergonomic handles (Fig. 1c) and a Storz three-dimensional (3D) imaging system (Karl Storz Endoscopy, Tuttlingen, Germany) (Fig. 1d). The 3D imaging system is based on two separate right and left video cameras that visualize the operative field, a computer that merges and accelerates the broadcasted frames from the two video cameras, and a video monitor with an active matrix covering its surface. The surgeon wears glasses that have a clockwise polarizing filter as the right lens and a counterclockwise polarizing filter as the left lens, and that allow a) b)

Aesop Robotic Surgical System
Fig. 2. The Automated endoscope system for optimal positioning (AESOP). a,b AESOP uses one mechanical arm with six degrees of freedom that is mounted on the operating table. c,d With AESOP, surgeons depend less on human assistants while performing laparoscopy

the left eye to see only images coming from the left camera while the right eye sees images from the right camera. This system causes a 3D image to be projected from the video monitor.

There are advantages and disadvantages of the ZEUS robotic system. Because the ZEUS components are mounted to the operating table, robotic adjustments relative to the patient are simplified. The open design of the ZEUS remote control unit also facilitates communication with scrubbed assistants. In addition, the availability of 3D imaging is advantageous for the system. Because new ZEUS instruments provide six DOFs, motion capabilities are better than those of standard laparoscopic instruments. Furthermore, many ZEUS instruments are already available, because designs are easily adapted from conventional laparoscopic instruments. On the other hand, the lack of an effective force-feedback feature is a disadvantage of ZEUS. Another disadvantage is the high initial capital investment for the robot, although ZEUS instruments are reusable.

Technical concerns have accompanied the introduction of master-slave systems. As with conventional laparoscopy, port placement is critical for successful robotic surgery. In general, ports should be arranged so the robot is best positioned for more challenging operative tasks (e.g., intracorporeal suturing). Optimal port placement for the ZEUS system can be affected by body habitus. For instance, if the distance between trocars is limited, performing ZEUSassisted procedures can become more difficult. These factors may become more problematic in smaller patients. As the distance between trocars decreases, the exchange and alignment of instruments can become tedious. On the other hand, the effectiveness of robotic motion can also become restricted as the abdominal wall thickness increases. Thus, more frequent robotic positioning may be warranted to optimize robotic function. With ZEUS, however, since all robotic arms are independently mounted on the operating table, adjustments to accommodate body habitus can be more straightforward than with the da Vinci system. Robotic installation can be time consuming with telerobotic systems. Proper robotic installation also impacts performance of the laparoscopic procedures. Regardless of the robotic system, mechanical arms should be installed to maximize the range of motion of the robotic instruments.

Scrubbed assistants are critical to the success of telerobotic procedures. After assisting with trocar placement and robot positioning, scrubbed assistants exchange instruments on the robotic arms. Assistants also use conventional laparoscopic instruments for introduction and /removal of sutures, countertrac-tion, suction, and assistance with hemostasis. The role of the assistant is especially important when non-robotic laparoscopic instruments are required (e.g., ultrasonic dissection, vascular stapling device, clip appliers, etc.). Most importantly, scrubbed assistants are immediately available if emergent laparotomy is required. Because of the distance separating the surgeon and the assistants, intraoperative communication can be impaired during telerobotics. In this regard, however, the open design of the ZEUS remote control unit may be advantageous to the periscope-type design of da Vinci.

As with conventional laparoscopy, a learning curve is present with telerobotic surgery. The robotic learning curve is thought, however, to be less steep than that of conventional laparoscopy. Since tactile feedback is essentially nonexistent with ZEUS and da Vinci, a learning curve exists for the performance of surgery preferentially with visual cues. In addition to suture breakage, lack of force feedback can also contribute to inadvertent tissue damage. A learning curve is also present when the magnified three-dimensional imaging systems are used, especially for surgeons accustomed to performing conventional laparoscopy on a standard video monitor [10]. The learning curve can be minimized by performing telerobotic procedures in familiar surroundings with the same team [11]. In the event the robot should fail, the surgeon should also have experience with intracorporeal suturing. In that case, the surgeon could finish with laparoscopy instead of converting to open surgery. Other groups, however, have evaluated the impact of using ZEUS for instructing medical students, surgical residents, and surgeons in advanced laparoscopic techniques [12-14]. In summary, these studies showed that, whereas robotic assistance conferred little or no advantage on the performance of simple tasks, suturing or other more complex tasks were accomplished with greater speed and precision when performed with ZEUS, regardless of the prior level of training of each surgeon. These data suggest that robotic assistance might facilitate the learning and performance of complex laparoscopic operations.

Laparoscopic Applications of ZEUS Renal and Adrenal

Robots have previously been utilized experimentally and clinically for upper urinary tract applications [13,15,16]. Gill et al. first reported the feasibility of laparoscopic telerobotic nephrectomy and adrenalectomy in the animal model using the ZEUS robot [13]. In that study, telerobotic procedures were compared with standard techniques for laparoscopic nephrectomy, and adrena-lectomy was performed in five farm pigs. The operative times were slower with robotics, but the adequacy of dissection and blood loss were equivalent [13]. Sung and Gill performed a head-to-head comparison of the da Vinci robotic system with the ZEUS robotic system for laparoscopic nephrectomy, adrenalec-tomy, and pyeloplasty [15]. Although feasibility was proven with each system, the operative times and learning curve were more favorable with da Vinci. Furthermore, the researchers concluded that operative motions were more intuitive with da Vinci [15]. The first telerobotic nephrectomy in humans was reported by Guillonneau et al. using the ZEUS robot [16]. All steps of telerobotic nephrectomy were successfully performed with an operative time of 200min and an estimated blood loss of less than 100ml [16]. To date, a larger experience with telerobotics for nephrectomy has not been reported. Although the feasibility of robotic adrenalectomy has also been reported with da Vinci in humans [17, 18], so far there is no report of robotic adrenalectomy with ZEUS.

Telerobotic laparoscopic pyeloplasty has also been performed clinically and in the animal model. The feasibility of laparoscopic pyeloplasty was first reported by Sung et al. using female farm pigs randomized to undergo surgery with or without the ZEUS robot [19]. When robotic and non-robotic procedures were compared, the differences in operative time, suturing time, and number of suture-bites per ureter were not significant [19]. In humans, robotic-assisted laparo-scopic pyeloplasty with both the da Vinci and the ZEUS robotic systems has been described [20,21]. In addition, when patients undergoing da Vinci-assisted laparoscopic Fengerplasty or Anderson-Hynes pyeloplasty were compared with patients undergoing the corresponding procedures without the robot, the da Vinci-assisted procedures were associated with shorter operative times and decreased suturing times [22]. To date, however, a large experience with ZEUSassisted pyeloplasties has not been reported.

Prostate

Given the difficulty of laparoscopic radical prostatectomy (LRP) and the incidence of prostate cancer, telerobotics has generated significant clinical interest among urologists. Guillonneau et al. [23] performed robotic-assisted, laparoscopic pelvic lymph-node dissection in 10 consecutive patients with T3M0 pro-static carcinoma and compared the operative, postoperative, and pathological parameters with the results from their last 10 patients undergoing conventional laparoscopic pelvic lymph-node dissection for similar indications by the same operator. The authors reported no specific intraoperative or postoperative complications in the robotic group. The mean operating time for the robotic group was 125 ± 57min (range, 75 to 215), significantly longer than that with conventional laparoscopic experience (p < 0.01). As for radical prostatectomy, Tewari and Menon recently reported excellent results for 250 cases of a robot-assisted radical prostatectomy using the da Vinci system [24]. The mean operating time for their robot-assisted radical prostatectomy was 2.5 h, and the average blood loss was 150 ml. Thus, the use of robot-assisted radical prostatectomy with the da Vinci system is now spreading. However, so far there has been no report on a robot-assisted radical prostatectomy using the ZEUS system. We recently performed an LRP assisted by the ZEUS robotic system. The ZEUS system was utilized only for vesicourethral anastomosis, one of the most difficult procedures to perform during LRP. The vesicourethral anastomosis using the ZEUS system, however, required 100min, which was not shorter than our average anastomosis time without ZEUS (data not shown). Since this is our first case with ZEUS, we believe that we can shorten the operation time as we increase our experience with the ZEUS system. The urethral catheter was removed 7 days after the operation without any postoperative complications. In our case, we utilized the ZEUS system only for vesicourethral anastomosis, whereas Tewari and Menon used the da Vinci system for all LRP procedures. We therefore cannot directly compare the two results. However, one of the disadvantages of the current robotic systems is lack of an effective force-feedback feature. The lack of tactile feedback can sometimes cause inadvertent tissue damage. Taken together, since the conversion to the ZEUS system from conventional laparoscopic surgery is easier than that to the da Vinci system, the utilization of the ZEUS system only for vesi-courethral anastomosis in LRP may become an alternative method to optimize the merit of the ZEUS system. After performing more LRP procedures using the ZEUS system, we will thus be able to better answer the question of which robotic system is most suitable for LRP.

Bladder

Although the first da Vinci-assisted laparoscopic cystectomy and ileal neoblad-der has been performed (personal communication, J. Binder, Frankfurt, Germany, 2002) based on the clinical experience with da Vinci-assisted LRP, so far there is no report of ZEUS-assisted laparoscopic cystectomy. In the animal model, Cho et al. have compared the performance of extravesical ureteral reimplantations with and without the ZEUS robotic system [25]. Procedures performed with the ZEUS robotic system required significantly more operative time, but all reimplantations were immediately water-tight, and the suturing characteristics were comparable between treatment groups. For robotic applications involving the lower urinary tract, additional clinical data are not available at this time.

Current Limitations and Future Perspectives

One of the major technical criticisms of robotic systems is that they are associated with a lack of tactile feedback from the operating instruments, which is only in part compensated for by the 3D visual feedback. This may be a temporary drawback, as technology evolves rapidly and significant research efforts are focusing on the issue of providing tactile feedback to robotic systems. Recently, a group of scientists in Spain has developed a robotic finger with a sense of touch. This robotic finger can feel the weight of what it is pushing and adjust the energy it uses accordingly [26]. This report is promising and suggests that in the foreseeable future, technologic advances may overcome, at least in part, the lack of tactile sensation characteristic of current robotic systems.

The feasibility and safety of robotic laparoscopy have been reported in clinical and experimental studies. Experiences in different centers, both clinically and experimentally, show that the use of the ZEUS system does not result in specific complications and achieves outcomes similar to those of standard laparoscopic procedures. It is a common finding, however, that the use of ZEUS increases the operative time. Furthermore, all clinical studies performed so far have failed to provide any evidence of specific patient benefits in general surgical procedures. Although the lack of verifiable clinical benefits may be frustrating, the demonstration of the feasibility and safety of using the ZEUS system for several surgical procedures should be seen as an encouraging starting point. The merging of robotics with computer technologies and virtual reality may also impact future generations of robots.

Telecommunication may also impact robotics. With current technology, tele-mentoring is an accepted discipline in laparoscopic surgery. The most important limitation on the performance of robotic-assisted procedures across long distances was considered to be the reliability (or quality of service) of telecommunication lines and the issue of latency (the delay from the time when the hand motion is initiated by the surgeon until the manipulator actually moves and the image is shown on the surgeon's monitor). Due to the latency factor, it was believed that the feasible distance for remote surgery was no more than a few hundred miles over terrestrial telecommunications [27]. With current telecommunications using dedicated asynchronous transfer mode (ATM) fibers, however, telerobotic surgery has been reported for human laparoscopic cholecystectomy between New York and Strasbourg, France [28]. The ZEUS system was used in all steps of that project. The mean time delay over transoceanic distances was 155 msec with the ATM fibers. This extremely short delay allowed the safe performance of remote laparoscopic cholecystectomy. With telecommunication and computing advances, the ease of telesurgery may increase, but clinical necessity remains unproven. The licensure and liability issues of telesurgery must also be resolved [29]. Cost is also a drawback at the moment. In spite of these limitations, however, the potential benefits of remote surgery are multiple. Many abdominal operations can indeed be performed laparoscopically now, but complex procedures are still in the hands of a limited number of experts. Remote robotic assistance may provide useful help to inexperienced surgeons in the early phase of the learning curve. Furthermore, patients will be able to receive the type of treatment best suited to their conditions, ideally in any part of the world. We will have to find out the best way to optimize the merit of the ZEUS system.

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