Text and Data Mining valid from 2018-07-10
Received: 17 March 2018
Accepted: 28 June 2018
First Online: 10 July 2018
Compliance with ethical standards
: The authors declare that they have no conflict of interest, nothing to declare.
: This is a retrospective study. Institutional review board approval was granted by means of a general waiver for studies with retrospective data analysis in each center. All procedures performed were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: Written informed consent to take part was given by all participants.