Received: 14 November 2017
Accepted: 30 January 2018
First Online: 21 May 2018
Ethics approval and consent to participate
: The Institutional Review Board approved this retrospective study and the requirement to obtain informed consent was waived. All data were handled in compliance with the Health Insurance Portability and Accountability Act of 1996.
: Not applicable.
: The authors declare that they have no competing interests.
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