Received: 4 July 2018
Accepted: 18 March 2019
First Online: 22 April 2019
Compliance with Ethical Standards
: The authors declare that they have no conflict of interest.
: All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008 (5).
: As it was a retrospective study, formal informed consent was not required.
: There was no external funding or grants that assisted in the study.