1Department of Surgery, Oulu University Hospital, Box 22, 90220 Oulu, Finland Tel.: +358-8-3152011, Fax: +358-8-3155318, , FI
2Department of Physical Medicine and Rehabilitation, Oulu University Hospital, Oulu, Finland, , FI
3Department of Surgery, Kainuu Central Hospital, Kajaani, Finland, , FI