Text and Data Mining valid from 2019-02-07
Received: 17 August 2018
Accepted: 23 January 2019
First Online: 7 February 2019
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: All procedures were performed in accordance with ethical standards of the institutional research committee and the 1964 Helsinki declaration and its later amendments.
: For such retrospective study, formal consent was not required.