Engineering Insight

Industrial robots that conform to Class 1 cleanroom requirements are the core components of an automated cell that mills patients' femurs to prepare them for the insertion of hip prostheses. Orto Maquet (Rastatt, Germany), a manufacturer of operating tables that has marketed the cell thus far in Germany and France, specified the RX 90 CR robot, developed by Stäubli (Horgen, Switzerland), for this application primarily because of its precision and repeatability.

Robots mill femurs 10 to 20 times more accurately than surgeons.

"Maquet claims that the robot drills the bone to an accuracy of 0.1 mm," says Jean-Luc Burquier, group division manager, robotics, at Stäubli's production unit in Faverges, France. "A surgeon typically achieves an accuracy of 1 to 2 mm, making the robot 10 to 20 times more accurate than its human counterpart." The machine's extraordinary precision results in less bleeding during the procedure and accelerates rehabilitation, which goes a long way toward allaying any misgivings the patient may have of being operated on by a robot, adds Burquier.

The RX 90 robot attracted the attention of Maquet engineers at the annual Hannover Fair trade show in Germany. "It is made of stainless steel and smooth polyurethane, making it suitable for use in Class 1 environments," notes Burquier. In addition, all of the cables and motors are embedded inside the arm, and the robot has a compact footprint. "We worked with Maquet for a couple of years to adapt the robot to their specifications and to incorporate additional safety features required by the application," adds Burquier.

The first operation using CASPAR (computer-assisted surgical planning and robotics) was conducted in 1997 in Germany. Maquet is currently exploring other applications, adds Burquier, and has achieved two world firsts: the replacement of cruciate knee ligaments in 1999, and the insertion of a tricompartment knee prosthesis. French and German hospitals are using CASPAR, and the cell will soon be installed in hospitals in Belgium and Italy. The company is seeking approval from US FDA to market the device in the United States.

For more information, contact Stäubli AG, See Str. 240, CH-8810 Horgen, Switzerland; phone: +41 172 52511; fax: +41 172 86211; Internet: http:// www.staubli.com.

—Norbert Sparrow