1. Department of Orthopaedic Surgery, University Hospital of Heidelberg, Schlierbacher Landstrasse 200a, 69118 Heidelberg, Germany
2. Institute of Medical Biometry and Informatics, University of Heidelberg, Im Neuenheimer Feld 305, 69120 Heidelberg, Germany
3. Adult Hip and Knee Service, Nuffield Orthopaedic Centre, Oxford University Hospitals NHS Foundation Trust, Windmill Road, Headington, Oxford OX3 7LD, UK
4. Orthopaedic Centre Paulinenhilfe, Diakonie-Klinikum Stuttgart, Rosenbergstraße 38, 70176 Stuttgart, Germany