1. Department of Orthopaedics and Traumatology, Freiburg University Hospital, 79106 Freiburg, Germany
2. Center for Orthopaedics, Trauma Surgery and Rehabilitation Medicine, Greifswald University Hospital, 17475 Greifswald, Germany
3. Spine and Scoliosis Center, Asklepios Klinik Wiesbaden, 65197 Wiesbaden, Germany