1. Department of Orthopaedic Surgery, University of Pennsylvania, 3400 Spruce Street, 2 Silverstein, Philadelphia, PA 19104, USA
2. Department of Orthopaedic Surgery, Penn Presbyterian Medical Center, Cupp 1, 39th and Market Streets, Philadelphia, PA 19104, USA
3. Department of Orthopaedic Surgery, Geisinger Medical Center, Danville, PA 17822, USA