Ren, Chengbo
Ji, Tianlong
Liu, Tingting
Dang, Jun
Li, Guang
Article History
Received: 3 March 2018
Accepted: 5 April 2018
First Online: 16 April 2018
Ethics approval and consent to participate
: This retrospective study was approved by the Regional Ethics Committee of our institution (approval number: SER-2017-9-2). The study was conducted in accordance with the Declaration of Helsinki.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.