1. Department of Physical Medicine and Rehabilitation, University of Colorado School of Medicine, Aurora, Colorado, USA
2. Craig Hospital, Englewood, Colorado, USA
3. Department of Orthopedics, University of Colorado School of Medicine, Aurora, Colorado, USA
4. Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, Palo Alto, California, USA
5. Department of Biostatistics & Informatics, University of Colorado School of Medicine, Aurora, Colorado, USA