1. Department of Orthopaedic Surgery, Rothman Orthopaedic Institute at Thomas Jefferson University Hospital, Philadelphia, PA
2. Department of Orthopaedic and Sports Medicine, Harborview Medical Center, University of Washington, Seattle, WA
3. Spine Unit, Sonnenhof Spital Bern, University of Bern, Bern, Switzerland
4. Center for Spinal and Scoliosis Surgery, Malteser Waldkrankenhaus St. Marien, Erlangen, Germany
5. Department of Orthopedics and Traumatology, Paracelsus Private Medical University Nuremberg, Nuremberg, Germany
6. Department of Orthopedic Surgery, University Medical Center, University of Utrecht, Utrecht, the Netherlands