1. Department of Cardiothoracic Surgery, Helsinki University Hospital, P.O. Box 340, 00029 Helsinki, Finland
2. Department of Orthopedics and Traumatology, Tampere University Hospital, P.O. Box 2000, 33521 Tampere, Finland
3. School of Medicine, Tampere University, 33104 Tampere, Finland
4. Research Unit, Centre of Laboratory, Tampere University Hospital, P.O. BOX 2000, 33521 Tampere, Finland