1. Orthopaedic Robotics Laboratory, Departments of Bioengineering and Orthopaedic Surgery, University of Pittsburgh, 408 Center for Bioengineering, 300 Technology Drive, Pittsburgh, PA 15219 e-mail:
2. Tokyo Metropolitan University, 6-6 Asahigaoka, Hino, Tokyo 191-0065, Japan
3. Orthopaedic Robotics Laboratory, Departments of Orthopaedic Surgery and Bioengineering, University of Pittsburgh, 408 Center for Bioengineering, 300 Technology Drive, Pittsburgh, PA 15219