1. Orthopaedic Biomechanics Laboratory, Midwest Orthopaedic and Minneapolis Medical Research Foundations
2. Department of Pathology Hennepin County Medical Centre, 914 South Eighth Street, 860C Minneapolis, Minnesota 55404, USA.
3. Department of Orthopaedic Surgery, Aarhus University Hospital, Aarhus Amtsyggehus, Tage-Hansens Gade, Aarhus C, Denmark.