1. Department of Bioengineering University of Pennsylvania 240 Skirkanich Hall, 210 S. 33rd Street Philadelphia PA 19104 USA
2. Translational Musculoskeletal Research Center Corporal Michael J Crescenz VA Medical Center 900 Woodland Ave Philadelphia PA 19104 USA
3. School of Biomedical Engineering, Science and Health Systems Drexel University 3141 Chestnut Street, Bossone 718 Philadelphia PA 19104 USA
4. McKay Orthopaedic Research Laboratory Department of Orthopaedic Surgery Perelman School of Medicine University of Pennsylvania 308A Stemmler Hall, 3450 Hamilton Walk Philadelphia PA 19104 USA