Received: 28 August 2017
Accepted: 11 January 2018
First Online: 23 January 2018
Ethics approval and consent to participate
: The study was approved by the ethic committee at the University Hospital Bonn (240/14). All patients gave written informed consent.
: Not applicable
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.