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 44649 Germany
2. Center for Rheumatology, Rheumazentrum Ruhrgebiet; Ruhr University of Bochum; Herne 44649 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 Bochum/Marien Hospital Witten; Herne 44649 Germany