1. Department of Orthopaedics, University of Gent, De Pintelaan 185B-9000 Gent, Belgium.
2. Division of Orthopaedic Surgery, 2626 White Oak Drive, Ann Arbor, Michigan 48103, USA.
3. Division of Orthopaedic Surgery, Mt Sinai Hospital, 600 University Avenue, Toronto, Ontario, Canada M5G 1X5.
4. Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8.