Received: 4 March 2020
Accepted: 5 May 2020
First Online: 15 May 2020
Ethics approval and consent to participate
: The study has been approved by the local Ethical Committee of the Ruhr-University Bochum (No. of approval 18–6260-BR). Due to the retrospective nature of this study there was no need for consent to participate.
: Not applicable.
: The authors declare that they have no competing interests.