Chlodwig Kirchhoff1
, Volker Braunstein2,3
, Jochen Paul1
, Andreas B Imhoff1
and Stefan Hinterwimmer1 
1
Department of Orthopedic Sports Surgery, Klinikum Rechts der Isar, Technische Universitaet, Ismaningerstrasse 22, D-81675 Munich, Germany
2
Department of Traumatology and Orthopedic Surgery – Campus Innenstadt, Ludwig-Maximilians Universitaet, Nussbaumstrasse 20, D-80336 Munich, Germany
3
AO Research Institute, Clavadelerstrasse 8, CH-7270, Davos, Switzerland