Funding for this research was provided by:
Received: 8 September 2020
Accepted: 5 May 2021
First Online: 19 May 2021
Change Date: 25 June 2021
Change Type: Correction
Change Details: A Correction to this paper has been published:
Change Details: https://doi.org/10.1186/S12891-021-04428-W
: All procedures performed involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Written informed consent was obtained from all individual participants included in the study. The study was approved by the Regional committee for Medical and Health Research Ethics in South East Norway (No.: 2013/2030).
: Not applicable.
: The authors declare that they have no competing interests.