Robotic surgery vs. computer-assisted surgery (CAS)

Robotic surgery

A surgical robot is a computer-controlled manipulator with artificial sensing reprogrammed to move and position tools to carry out surgical tasks. It assists the surgeon in carrying out repetitive motions automatically, relieving the surgeon of a tiring task. A surgical robot can position its tools accurately at a pre-defined location or move them with micro motions or through a complex path.

These features and benefits are equally applicable to computer-assisted surgery (CAS), which uses computer technology for surgical planning and guiding or performing surgical interventions. However, robots provide greater accuracy and precision than CAS. However, due to their ability to constrain the tools, robots are much superior to CAS.

In CAS, a surgeon holds the tools and could ignore all warnings to the contrary and cut into unsafe regions. On the other hand, the robots can be programmed to prevent motions into critical regions or only allow motions along a specified direction. Thus, the robots are considered safe and enhance the safety of the procedure compared with conventional surgery and CAS.

The main difference between robotic and computer-assisted surgery is that robots are moved by some sort of motorized system while computer-assisted systems are generally manually powered by the surgeon.

In surgery, the majority of computer-based systems are tracking systems. These may be used to track tools or parts of the anatomy, either using a sensor-based system or clamping the tool onto a manipulator arm whose joints are monitored for the position. The sensor-based systems usually use an array, either of light-emitting diodes (LEDs) or optical reflectors, attached to the tool. A group of cameras can track the position and orientation of the array in three-dimensional space. The tool and its three-dimensional coordinates can then be represented on a computer screen concerning the coordinates of the target anatomy, which is also represented.

The CAS systems, unlike robots, rely on the surgeon for motive power. However, they too are vulnerable to hardware and software errors in the data provided by the tracking systems for the tools and tissue. The surgeon must detect a problem and take corrective action or stop the procedure. In addition, just as for robotic surgery, most CAS systems use a pre-operative planning system. It allows the surgeon to take patient images, form them into three-dimensional models and display them on a computer with the various tool locations. The surgeon can then simulate the whole procedure and ensure that the proposed protocol is correct, removing worry and strain from the actual operation. The safety issues for pre-operative planners in both CAS and robots are broadly similar.

Compared with CAS systems, the potential benefits available to a well-designed robotic surgery system are:

  • The ability to move in a predefined and reprogrammable complex three-dimensional path, both accurately and predictably.
  • The ability accurately and repeatedly to position and orientate at a reprogrammable point or a series of points. Although CAS systems may also have this ability, robot accuracy is generally higher.
  • The ability to make repetitive motions, for long periods, tirelessly.
  • The ability to move to a location and hold tools there for long periods accurately, rigidly, and without tremors.
  • The ability actively to constrain tools to a particular path or location, even against externally imposed forces, thus preventing damage to vital regions. It can lead to safer procedures than those achieved using CAS.
  • To be able to move, locate and hold tools within hazardous environments without damage to the surgeon (e.g., from fluoroscopic or radioactive sources).
  • To be able to make precise micro motions with prespecified micro forces.
  • To respond and adapt very quickly and automatically, either in response to sensor signals or changes in commands.
  • To perform ‘keyhole’ minimal access surgery without the aid of vision and without ‘forget- ting’ the path or the location.

In short, robots have the very useful property of constraining and guiding surgical interventions in a way that is not possible with normal CAS systems. Robots can be autonomous and carry out repetitive actions tirelessly, as well as move through complex paths with considerable accuracy.

However, since they tend to involve additional components for the system, robots will inevitably make the equipment costlier and complex than CAS systems. This cost and complexity will be easier to justify in those procedures where the benefits of robotic interventions provide a clear advantage over CAS.