1. Department of Children’s Orthopaedics, Deformity Correction and Foot Surgery, Münster University Hospital, Albert-Schweitzer-Strasse 33, D-48149 Münster, Germany.
2. Department of Pediatric Orthopaedics and Neuroorthopaedics, Evangelische Stiftung Volmarstein, Lothar-Gau-Strasse 11, D-58300 Wetter, Germany.