1. Department of Biomaterials Research, Institute of Surgical Sciences, University of Gothenburg, SE-413 90, Gothenburg
2. Department of Orthopaedics, Sahlgrenska University Hospital, University of Gothenburg, SE-413 45, Gothenburg
3. Department of Orthopaedics, Östra Hospital, SE-416 85, Gothenburg
4. Department of Orthopaedic Surgery, Karolinska Hospital, SE-171 76, Stockholm, Sweden