1. Department of Physiology and Technology, National Institute for Working Life, Box 7654, S‐907 13 Umeå,
2. Department of Anatomy, Umeå University, Umeå,
3. Department of Biomedical Engineering, Umeå University, Umeå,
4. Department of Rehabilitation Medicine, University of Linköping, and,
5. Department of Hand Surgery, University of Gothenburg, Sweden