1. Southern California Permanente Medical Group, Department of Orthopaedics, Fontana Medical Center, Los Angeles, CA, USA.
2. New York University Langone Orthopedic Hospital, New York, NY, USA.
3. Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA.
4. Department of Internal Medicine, Highland Hospital, Oakland, CA, USA.