1. Department of Orthopaedic Surgery, König-Ludwig-Haus, Julius-Maximilians-University, Würzburg, Germany
2. Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, Pennsylvania and Cartilage Biology and Orthopaedics Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland
3. Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, Pennsylvania