1. Helios ENDO-Klinik, Hamburg, Germany
2. Department of Orthopedics and Geriatric Sciences, Catholic University of the Sacred Heart, Rome, Italy
3. Department of Public Health, Orthopedic Unit, “Federico II” University, Naples, Italy
4. Department of Experimental Surgery, Center for Clinical Research, Ruhr-Universität, Bochum, Germany
5. Musculoskeletal Oncology Unit, Department of Orthopedics, University of Florence, Florence, Italy
6. Medac GmbH, Wedel, Germany