1. Department of Surgery, University of Washington, Seattle, Washington.
2. Surgical Outcomes Research Center, University of Washington, Seattle, Washington.
3. Rainier Orthopedic Institute, Proliance Surgeons, Inc., Puyallup, Washington.
4. Swedish Neuroscience Institute, Swedish Medical Center, Seattle, Washington.
5. Department of Neurosurgery and Orthopaedics, Virginia Mason Medical Center, Seattle, Washington.
6. Department of Health Services, University of Washington, Seattle, Washington.
7. Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, Washington.
8. Department of Orthopaedic Surgery, University of Chicago Medical Center, Chicago, Illinois.
9. Department of Orthopaedic Surgery, University of California, Irvine, California.
10. Department of Orthopedics and Rehabilitation, University of Wisconsin, Madison, Wisconsin.