Received: 6 July 2020
Accepted: 19 May 2021
First Online: 12 June 2021
: The study protocol was approved by the Ethics Committee of the University of Wuppertal (MS/JE 29.11.11).
: Not applicable.
: The authors, Christian Baumgart, Eduard Kurz, Jürgen Freiwald, and Matthias Wilhelm Hoppe, declare that they have no competing interests.