1. Department of Orthopaedics, Erasmus Medical Center, Rotterdam The Netherlands
2. Department of Orthopaedics, Leiden University Medical Center, Leiden The Netherlands
3. Depatment of Orthopaedics, University of Groningen, University Medical Center Groningen, Groningen The Netherlands
4. Department of Orthopaedics, Hagaziekenhuis, The Hague The Netherlands