1. Department of Orthopedic Surgery, Beth Israel Deaconess Plymouth, Plymouth, Massachusetts, United States
2. Department of Orthopedic Surgery, Emory University, Atlanta, Georgia, United States
3. Department of Neurosurgery, Duke University, Durham, North Carolina, United States
4. Department of Orthopedic Surgery, Rothman Institute, Philadelphia, Pennsylvania, United States
5. Department of Neurosurgery, Rush University, Chicago, Illinois, United States
6. Piedmont Hospital, Atlanta, Georgia, United States