1Orthopaedic Research Laboratories, Department of Surgery, 375 MSRB, Box 3093, Duke University Medical Center, Durham, NC 22710 USA
2Department of Biomedical Engineering, University of Cincinnati, 2901 Campus Drive, Cincinnati, OH 45221-0048 USA
3Orthopaedic Research Laboratories, University of Michigan, Room G-161, 400 North Ingalls, Ann Arbor, MI 48105-0486 USA
4Department of Biologic and Materials Sciences, University of Michigan, 1011 North University Avenue, Ann Arbor, MI 48109-1078 USA