ISRACAS'2000 -- Invited Presentation

Prof. J.C. Bowersox, MD, PhD, FACS

Department of Surgery
U. of California, San Francisco, USA

When the potential of telesurgery was first introduced to surgeons in 1995, few believed that robotic systems would actually be used to operate on humans. It was hard to imagine that an electromechanical device could replicate the precise motions necessary for dynamic tissue handling, and concerns were raised regarding safety and patient acceptance. Less than three years later, the first clinical use of a surgical telemanipulator occurred in France, when surgeons working from a console positioned across the operating room repaired a damaged heart valve. Since then, more than one hundred patients have undergone surgery with the assistance of robotic surgical systems. The successful introduction of surgical telemanipulators has been based on the coordinated development in three key areas: system design, user validation, and clinical need.

System design: Remote teleoperation has been used in hazardous material handling for almost fifty years. Consequently, the principles of master-slave manipulators were well described when telesurgery development began in the 1980s. The forces and working volumes required for precision handling of living organs, however, are substantially different from those used in industrial applications. Thus, in the telesurgery program started at Stanford Research Institute (SRI International), under the direction of Phil Green, robotic manipulators and control systems were specifically designed for use in operating rooms, on delicate tissues. Equally critical was the design of the user interface. Soft tissue surgery is performed in a complex and dynamic task environment. Three-dimensional spatial orientation is necessary for precision tissue handling, as are haptic cues including perception of tissue mass and elasticity, and instrument forces. Proper eye-hand orientation (oculovestibular axis) must be maintained to create a natural, intuitive work environment. These principles were incorporated into the surgeon's console of the SRI Telepresence Surgery System. The operator looks down at a mirrored screen, on which a three-dimensional image of the remote environment is projected. Hands are place in standard surgical instrument handles attached to the manipulator masters. Surgical instrument tips, attached to the manipulator slaves, are oriented in a manner to appear as though they are extending from the surgeon's hands. Gravity compensation and force feedback are incorporated, closely approximating the feel of instruments encountered in the operating room. The integrated user interface instills a sense of immersion in the remote environment, allowing existing surgical skills to be applied without special training or practice.

User Validation: The potential of remote telepresence surgery was demonstrated in a series of experiments on live, anesthetized swine, using a prototype four degree-of-freedom telemanipulator system. Procedures were chosen to replicate the range of task elements encountered in soft tissue surgery. These fundamental maneuvers included incision, grasping, dissection (tissue spreading and cutting), suturing, and knot tying. Surgeons performed common operations, including organ removal (cholecystectomy, nephrectomy), blood vessel repair and replacement, catheter manipulation, and intestinal anastomoses, operating from a remote console. All procedures were completed successfully, without complications. Procedures required 2.5-2.8 times as long to complete using the telemanipulator, compared with conventional surgical techniques. A four degree-of-freedom, remote center-of-motion system was designed for minimally invasive surgery. Using the same intuitive operator interface, intracorporeal suturing and knot tying, as well as tubular anastomoses, were performed under ex vivo conditions. Performance was significantly better than that achieved using standard laparoscopic techniques for all task conditions. More recently, a prototype micromanipulator has been developed, and used in experimental microvascular procedures. Again, from the same operator interface, surgeons were able to view highly magnified, stereoscopic images of 1 mm diameter rat femoral arteries, and perform precise, end-to-end anastomoses using standard microsurgical techniques.

Clinical Need: The rapid progression of telesurgery from prototype demonstration to clinical application was based on evidence that patients recovered more rapidly, with fewer complications, from minimally invasive surgery. Loss of intracorporeal wrist motion, and the unnatural orientation of video displays and instrumentation have created a challenging environment for surgeons. For straightforward procedures, not requiring suturing or complex tissue manipulations (eg, gallbladder removal), minimally invasive techniques have been widely adopted. Special training, frequent practice, and lengthy operating times are required for more complex laparoscopic procedures, including suturing and knot tying, and have limited their application to relatively few centers and surgeons. By restoring wrist motion at the tissue level, and a natural work orientation, commercially-developed surgical telemanipulators offer surgeons an opportunity to apply minimally invasive techniques to more challenging cases, such as myocardial revascularization and valve repair. To date, the use of robotic systems in cardiac surgery has been described in more than a dozen peer-reviewed articles from Europe and North America. Approval to market such systems has been received in Europe, and clinical trials are underway in the Untied States, Canada, and Japan.

Future opportunities for surgical telemanipulator development include component miniaturization, directed energy delivery, and special purpose instrumentation. Microscale, six degree-of-freedom instruments are needed for fetal, congenital heart, and neonatal surgery. Alternative approaches to suturing and knot tying for joining tissues, such as laser welding or biological gluing, would increase telemanipulator value. Finally, less versatile, but less expensive systems could be developed for specialized applications, such as ophthalmic procedures, and image guided tumor biopsy or ablation.