1. Truven Health Analytics and Health Care Policy, Harvard Medical School, Ann Arbor, Michigan
2. Department of Rehabilitation Medicine, University of Washington, Seattle3Department of Orthopaedics and Sports Medicine, University of Washington, Seattle4Department of Neurological Surgery, University of Washington, Seattle
3. Department of Neurology, Michigan NeuroSport, University of Michigan, Ann Arbor
4. School of Kinesiology, Michigan NeuroSport, Michigan Injury Center, University of Michigan, Ann Arbor