1. Center for Spine Surgery and Pain Therapy, Center for Orthopedics and Traumatology of the St. Elisabeth Group – Catholic Hospital Rhein-Ruhr, St. Anna Hospital Herne/Marien Hospital Herne University Hospital of the Ruhr University of Bochum/Marien Hospital Witten, Herne, Germany
2. Center for Rheumatology, Rheumazentrum Ruhrgebiet, Ruhr University of Bochum, Bochum, Germany
3. Center for Orthopedics and Traumatology of the St. Elisabeth Group – Catholic Hospital Rhein-Ruhr, St. Anna Hospital Herne/Marien Hospital Herne University Hospital of the Ruhr University of Bochum/Marien Hospital Witten, Herne, Germany
4. Center for Spine Surgery and Pain Therapy, Center for Orthopedics and Traumatology of the St. Elisabeth Group – Catholic Hospital Rhein-Ruhr, St. Anna Hospital Herne, University of Witten/Herdecke, Herne, Germany