Active Autonomous Robotic Knee and Hip Replacement - Early Results

Introduction: Malalignment of knee and hip implants has been shown to increase loosening and revision rates. Navigation has lowered these. Active robotic surgery, with submillimeter precision planning by the surgeon and autonomous execution by a robot, can be the next step in this process. We report early results of robotic knee and hip replacements.

Methods: Patients undergoing a primary knee replacement or posterior approach hip replacement were offered robotic surgery. A CT scan was used for three-dimensional planning. Plan was saved to robot. After exposure, robot was attached to patient with pins. For knees, femur and tibia were registered and robot performed autonomous milling of both bones. For hips, femur and acetabulum were registered, robot milled the femur and guided the surgeon for acetabular reaming. Patients were followed with Knee Society Scores or Harris Hip Scores and radiographs.

Results: For knees, femoral and tibial registration was completed in 5/5 patients. Milling was completed in all femora and 4/5 tibiae. Size and position were as planned for all implants. Knee Society Scores and Functional Scores changed from 40 and 55 to 53 and 35 at a mean of 6 weeks, respectively. There were no early complications.

For hips, femoral registration and milling was completed in 5/5 patients; 3/5 patients received the planned size stem. Acetabular registration and reaming was completed in 3/5 patients; guided implantation was completed in 1/5. Cup size was as planned in 4/5 patients. Harris Hip Scores increased from 45 to 72 at a mean of 13 weeks. There was one subsidence and one periprosthetic fracture.

Conclusion: Active robotic surgery for TKA is under investigation, and appears feasible and safe for THA. Early results are promising, currently more consistent in knees than in hips. Continued software evolution will make the learning curve shorter, particularly for hips.