1. Department of Orthopaedic Surgery, Copenhagen University Hospital, Hvidovre, Denmark
2. Department of Orthopaedics, Sahlgrenska University Hospital, Gothenburg, Sweden
3. Department of Orthopaedics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Sweden
4. Harris Orthopaedic Laboratory, Department of Orthopaedics, Massachusetts General Hospital, Boston, USA