1. Department of Biomedical Engineering; 1101 Beal Ave. University of Michigan; Ann Arbor MI 48109-2099 USA
2. Materials Science Program; University of Wisconsin; Madison WI 53706 USA
3. Department of Biomedical Engineering; University of Wisconsin; Madison WI 53706 USA
4. Department of Orthopedics and Rehabilitation; University of Wisconsin; Madison WI 53706 USA
5. Department of Mechanical Engineering; University of Michigan; Ann Arbor MI 48109-2125 USA
6. Department of Surgery; University of Michigan; Ann Arbor MI 48109-032 USA