Mats Grönblad1, Markku Hupli1, Pekka Wennerstrand1, Erkki Järvinen1, Asko Lukinmaa1, Jukka-Pekka Kouri1, Erkki Karaharju1
1Spine Research Unit, Clinical Research Institute and Departments of Physical Medicine and Rehabilitation and Orthopaedics and Traumatology, Helsinki University Central Hospital, Helsinki, Finland