Received: 5 February 2019
Revised: 10 December 2019
Accepted: 22 January 2020
First Online: 30 January 2020
Compliance with ethical standards
: CEH has received royalties from Medacta Int. GO has given paid lectures for Medtronic and Stryker. The other authors declare that they have no competing interests. There was no external funding for this study.