Received: 9 June 2018
Accepted: 27 September 2018
First Online: 12 October 2018
Ethics approval and consent to participate
: This retrospective study was performed with the approval of the institutional review board (Department of Orthopaedic Surgery, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences. Project number 941), and all patients signed the consent form drafted for the study.
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.