1. Division of Pharmacoepidemiology and Pharmacoeconomics, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02120, USA.
2. Department of Orthopaedic Surgery, Rehabilitationskrankenhaus Ulm University of Ulm, 89081 Ulm, Germany.
3. Department of Epidemiology, German Centre for Research on Ageing, 69115 Heidelberg, Germany.
4. Medical Research Council’s Research Collaboration, Department of Social Medicine University of Bristol, Bristol BS8 2PR, UK.
5. Department of Orthopaedic Surgery University of Dresden, 07307 Dresden, Germany.