1. The Micheli Center for Sports Injury Prevention, Waltham, Massachusetts.
2. Division of Sports Medicine, Department of Orthopaedics, Boston Children's Hospital, Boston, Massachusetts.
3. Brain Injury Center, Boston Children's Hospital, Boston, Massachusetts.
4. Department of Orthopaedic Surgery, Harvard Medical School, Boston, Massachusetts.
5. Department of Pediatrics, Harvard Medical School, Boston, Massachusetts.