Text and Data Mining valid from 2018-08-04
Received: 2 May 2018
Accepted: 31 July 2018
First Online: 4 August 2018
Compliance of 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 (Ethikkommission, Med. Univ. Innsbruck; 2009-02-20). 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.
: For this type of study formal consent is not required.