1. From the Departments of Surgery, University of Umeå, S-90185, S-90185 Umeå, Sweden
2. Christer Hildingsson Dept. of Orthopedics University of Umeå S-90185 Umeå Sweden
3. From the Departments of Orthopedics, University of Umeå, S-90185, S-90185 Umeå, Sweden