1. Hip Preservation Center, Division of Sports Medicine, Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois, USA
2. Division of Sports Medicine, Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
3. Division of Sports Medicine, Department of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina, USA
4. Division of Sports Medicine, Department of Orthopaedics, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA