1. Translational Musculoskeletal Research Center, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA 19104, USA.
2. McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
3. School of Biomedical Sciences, Drexel University, Philadelphia, PA 19104, USA.
4. Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19348, USA.
5. Department of Neurosurgery, University of Pennsylvania, Philadelphia, PA 19104, USA.
6. Department of Biomedical Engineering, University of Delaware, Newark, DE 19716, USA.
7. Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA.