1. Department of Orthopaedics and Traumatology, University Hospital Basel, Basel, Switzerland
2. Clinic of Orthopaedic Surgery, Kantonsspital Baselland, Liestal, Switzerland
3. Hip Department, IRCCS Galeazzi Orthopaedic Institute, Milano, Italy
4. Orthopaedic Department, Charité – Universitätsmedizin Berlin, Berlin, Germany