Document is current

Article History

Received: 14 December 2017

Accepted: 18 April 2018

First Online: 27 April 2018

Ethics approval and consent to participate

: This study was performed in agreement with the declaration of Helsinki and in accordance with a vote from the ethical committee of the Private University of Witten/Herdecke (75/2013). Due to this vote no written informed consent was required for the present study, and no further permissions were required. This is in accordance with German National law (Medizinproduktegesetz (MPG) §24).

: All authors declare that they have no competing interests.

: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.