Received: 14 May 2020
Accepted: 4 June 2021
First Online: 3 July 2021
: This retrospective study was conducted in compliance with the tenets of the Declaration of Helsinki of 1964 and its subsequent amendments. Furthermore, the use of the BSTT database was approved by the Institutional Review Board of the Japanese Orthopedic Association.Because the database is de-identified, informed consent was not mandated by the Ethics Guidelines for Human Subject Medical Research, and the requirement for informed consent was waived by the Institutional Review Board.
: Consent for publication must be obtained from that person, or in the case of children, their parent or legal guardian.
: The authors declare that they have no competing interests.