1. Department of Orthopaedic Surgery, University of California, San Francisco, CA 94110-1342, USA;
2. Department of Biomedical Engineering, Jonsson Engineering Center, Rensselaer Polytechnic Institute, Troy, NY 12180-3590, USA;
3. Faculty of Dentistry, Université de Montréal, Canada; and
4. Department of Plastic and Reconstructive Surgery, Stanford University, 257 Campus Drive, Room GK207, Stanford, CA 94305, USA