Text and Data Mining valid from 2018-11-16
Received: 8 August 2018
Accepted: 31 October 2018
First Online: 16 November 2018
: Not applicable.
: The study was approved by the local Data Protection Official for Research at Oslo University Hospital, and by the Regional Committee for Medical and Health Research Ethics. According to this approval consent to participate was not required in this retrospective study.
: The images submitted are entirely unidentifiable. According to the approval by the local Data Protection Official at Oslo University Hospital consent for publication was not required.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.