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Address reprint requests to Ralph J. Damiano, Jr, MD, Division of Cardiothoracic Surgery, One Barnes-Jewish Hospital Plaza, Queeny Tower, Suite 3108, St. Louis, MO 63110
Affiliations
From the Division of Cardiac Surgery, Washington University School of Medicine, St. Louis, MO
Robotic surgical systems have recently been introduced into clinical cardiac surgery. They have been used to perform a wide range of procedures including coronary artery bypass grafting, mitral valve repair and replacement, atrial septal defect closure, and patent ductus arteriosus ligation.
These sophisticated systems have been used in an attempt to decrease the invasiveness of cardiac surgery and hold the promise of enabling endoscopic cardiac procedures. Despite numerous attempts over the last decade, manual endoscopic cardiac surgery has proven impossible due to the many shortcomings associated with conventional endoscopic instrumentation. The principal problem is that the lengths of endoscopic instruments magnify even the slightest tremor, making microsurgery extremely difficult. Another problem occurs because these instruments must be introduced through ports. A fixed pivot point at the chest wall causes a fulcrum effect, making it difficult to precisely judge the deflection of the instrument tip for a prescribed movement of the instrument handle. Finally, the nonintuitive movement of endoscopic tools (i.e., the instrument tip moving in the opposite direction of the handle) becomes more problematic in microscopic suturing. As a result of these limitations, the loss of depth perception due to conventional endoscopy, the limited access to target vessels, and the absence of force feedback, it is not surprising that there are few endoscopic applications in microsurgical disciplines.
Robotic surgical systems have been developed principally to assist in microsurgery. Development of the Computer Motion system (Computer Motion, Inc., Goleta, CA) began in 1992. A voice-controlled robotic arm to hold a camera (Aesop) was first introduced into clinical practice in 1994. Since then, this robotic arm has been used to assist in more than 125,000 cases. The ZEUS robotic microsurgical system was then developed and was introduced into clinical use in October 1998. The first clinical case involved coronary bypass grafting by Dr. Reichenspurner's group in Munich.
This involved endoscopic left internal thoracic artery to left anterior descending bypass grafting in a patient undergoing open chest surgery. Since its introduction, the ZEUS system has been used in more than 300 cases, including more than 110 coronary bypass graft procedures, 80 internal mammary takedowns, 3 ligations of patent ductus arteriosus, and several mitral valve repairs. The robotic system is presently being used at more than 40 sites worldwide.
The Computer Motion system has three main components: a surgeon console, a computer controller, and specially designed instrument tips attached to robotic arms (1, 2). The console consists of a video monitor and two custom instrument handles that resemble those of traditional microsurgical instruments. The surgeon sits at the console and manipulates these instrument handles; his or her motions are relayed mechanically to a computer controller. These motions are then digitized, and with specially designed software filtered and scaled. This information is then relayed in real time to robotic arms attached to the operating room table. These arms hold specially designed endoscopic instruments that are placed through 5-mm ports. A third robotic arm is used to control the endoscope. This arm is under direct voice control, and responds to a set of more than 20 simple commands.
The power of robotically assisted surgical systems is the incorporation of a digital interface between the instrument handle and tip. The computer software is able to manipulate the digitized surgeon's movements to enhance dexterity. The other dramatic difference from open surgery is that the surgeon visualizes the operative field on a video monitor. This provides a number of important advantages for this new operative environment.
Endoscopy provides better magnification and improved visualization. Traditional open procedures are performed with the assistance of surgical loupes. Magnification typically is 2.5x to 3.0x. However, much greater magnification (10- to 20-fold) can be achieved with a standard endoscope. When working on small coronary vessels, this extra magnification can enhance anatomic detail and facilitate microsuturing.
A drawback to endoscopy has been the loss of depth perception with standard two-dimensional video monitors. Our own work has shown that in complex drills, three-dimensional vision does improve performance. This has been supported by others.
Although the Computer Motion system originally came with a standard two-dimensional monitor, it now offers optional high-resolution three-dimensional video.
Endoscopic visualization also has been improved by the development of a robotic arm (Aesop) that manipulates the endoscope. Voice-activated camera control eliminates the need for an assistant, and the robotic arm holds the camera steadier than is humanly possible. Kavoussi et al.
found that when a robotic arm is used, the requirements for camera lens cleaning during procedures are reduced by three- to five-fold. The robotic arm is more stable and precise than manually guided assistance, and ideal camera positions can be saved and returned to with a simple command. In our specialty, this robotic arm has been proven helpful in facilitating both valve surgery and internal thoracic artery takedown.
The most important advantage of computer-assisted surgery is enhanced surgical dexterity. Involuntary tremor can be a significant hindrance to microsurgery, especially when working in a magnified field with endoscopic instruments. Robotic systems eliminate this problem. By using a computer controller to digitize surgical movement, high-frequency motion is filtered, allowing the surgical movement to be translated into a smooth movement free of tremor. Another advantage of robotically assisted surgery is the computer's ability to scale the surgeon's movement. This allows for gross hand movements at the console to be translated into fine movements of the robotic instruments at the operative site. Custom-designed software controls the degree of scaling from 1:1 to 10:1, depending on the surgeon's preference. As magnification increases, scaling can be increased, allowing the surgeon to feel that he or she is being shrunk down into the operative field. This scaled telepresence may enable surgeons to operate comfortably on extremely small structures.
The Computer Motion system also allows for improved instrumentation compared to conventional endoscopic instruments. Surgical instruments can be custom made to fit on the robotic arms. Instruments identical to those used for traditional coronary bypass grafting are used for these procedures (3, 4, 5). Specially designed scissors, graspers, scalpels, and needle holders are available. Although the current system has only four degrees of freedom, the new Microwrist system will have an additional degree of freedom inside the patient, allowing for enhanced dexterity (Fig 6). Unfortunately, the currently available system does not have haptic feedback. The loss of sense of touch is partially overcome by the enhanced visualization, but we hope that future advanced systems will include this feature.
The robotic surgical system also provides better ergonomics. In traditional endoscopic surgery, the surgeon is required to stand at the operating room table, often in awkward positions. Video monitors across the table are not always positioned appropriately for direct, unobstructed viewing. As a result, surgeons often complain of fatigue during these operations. In robotically assisted surgery this is avoided, because the surgeon can be comfortably seated in front of the console. An ergonomically designed chair is used to reduce physical fatigue. It is hoped that this will maintain surgeon performance at optimal levels for longer periods.
The combination of better visualization, improved dexterity, better instrumentation, and reduced fatigue allows for a level of precision superior to that afforded by conventional endoscopy. This has now been proven in clinical experience. Robotic systems have enabled surgeons around the world to perform endoscopic coronary artery bypass grafting, a procedure impossible to perform by hand. This is the most striking demonstration of the ability of these systems to enhance surgical dexterity. The future of robotically assisted surgery is bright. As these systems become easier to use and more affordable, we predict that they will have an ever-increasing impact on our surgical discipline.
References
Prasad SM
Ducko CT
Stephenson ER
et al.
Prospective clinical trial of robotically assisted endoscopic coronary grafting with 1-year follow-up.
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