FIRST CLINICAL TRIALS OF A “HANDS-ON” ACTIVE CONSTRAINT ROBOT

Abstract

The Acrobot®, an active constraint “hands-on” robotic system, gives navigation cues to the surgeon, and also assists him in the surgery, using active software constraints if he tries to depart from the preoperative plan. It has just entered clinical trials. We report the first 5 cases.

The Acrobot® system for precision total knee arthroplasty comprises the following components:

• 1. A CT-based planning system

• 2. The limb positioning system

• 3. The Acrobot’s hardware components:

• a gross positioning device with separate brakes and encoders, locked off for safety during the procedure,

• a fully back-driveable low force robot, and

• a force control handle on the robot close to the high-speed milling tool.

• 4. The Acrobot’s software which:

• imports the preoperative plan,

• allows anatomic registration

• provides navigation,

• physically assists the surgeon perform his plan

Each patient’s knee scores were monitored and postoperative CT scan was compared with the preoperative plan.

Seven robot assisted arthroplasties have been performed. No significant complications have been encountered. The Knee and Womac Scores show that the procedure is safe and comparable to conventional surgery in the early postoperative period. The envelope of error on postoperative CT scans has been within the accuracy of the method of measurement, at < 1 mm and < 10 without the outliers which haunt every clinical series.

The Acrobot® system for total knee arthroplasty has completed its preliminary trial satisfactorily. It provides a handson operation but with robotic levels of accuracy. It is suitable for conventional open surgery, but its real place will be in the arena of minimally invasive unicondylar knee arthroplasty, hip arthroplasty and resurfacing, and in the spine, where active constraint will prevent potentially dangerous surgical errors.