F Köckerling1, D Adolf2. 1. Department of Surgery and Center for Minimally Invasive Surgery, Academic Teaching Hospital of Charité Medical School, Vivantes Hospital, Neue Bergstrasse 6, 13585, Berlin, Germany. ferdinand.koeckerling@vivantes.de. 2. StatConsult GmbH, Halberstädter Strasse 40a, 39112, Magdeburg, Germany.