1. Department of Orthopaedics and Traumatology, Helsinki University Hospital, Helsinki, Finland
2. Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital, and Department of Applied Physics, University of Kuopio, Kuopio, Finland
3. Department of Orthopaedics, Güteborg University, Gothenburg, Sweden
4. Department of Surgery, Jyväskylä Central Hospital, Jyväskylä, Finland