1. Department of Neurological Surgery, Washington University School of Medicine, Saint Louis, Missouri, USA;
2. Current Affiliation: University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
3. Department of Orthopedic Surgery, New England Baptist Hospital, Boston, Massachusetts, USA;
4. Department of Orthopedic Surgery, University of Maryland Medical System, Baltimore, Maryland, USA;
5. Department of Orthopedic Surgery, Washington University School of Medicine, Saint Louis, Missouri, USA;