ORTON Orthopaedic Hospital, Invalid Foundation, Helsinki, Finland
Sponsorship: This study was supported by Fortum (Neste).
Correspondence and requests for reprints to Mauno Ylikoski, ORTON Orthopaedic Hospital, Invalid Foundation, Tenholantie 10, FIN-00280 Helsinki, Finland
Tel: +358 9 4748 6238; fax: +358 9 4748 2401;
e-mail: [email protected]