1. Department of Orthopaedics, Sahlgrenska University Hospital, 413 45, Göteborg Sweden
2. Department of Women and Child Health, Karolinska Institutet, Stockholm Sweden
3. Kennedy Krieger Institute, Baltimore, MD USA
4. Department of Orthopaedics, Walter Reed Army Medical Center, Washington, DC USA
5. Department of Orthopaedics, Johns Hopkins Hospital, Baltimore, MD USA
6. Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm Sweden