Received: 21 June 2019
Accepted: 15 October 2019
First Online: 8 November 2019
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: All the procedures involving human participants were performed in accordance with the ethical standards of the institutional research committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.
: For this retrospective study, formal consent was not required.