1. Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA.
2. Department of Orthopaedic Surgery, Georgetown University Medical Center, Washington DC, USA.
3. Department of Orthopaedic Surgery, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.
4. Department of Orthopedic Surgery, University of Texas Health Science Center at Houston, Houston, Texas, USA.