1. Norrlandskliniken, Umeå and Umeå University, Department of Surgical and Perioperative Sciences, 901 87 Umeå, Sweden
2. Pain Rehabilitation, Norrlands University Hospital, Umeå 901 85, Sweden
3. Norrlandskliniken, Glimmervägen 5E, 907 40 Umeå, Sweden
4. Umeå University, Department of Community Medicine and Rehabilitation, 901 87 Umeå, Sweden