Text and Data Mining valid from 2018-08-11
Received: 22 February 2018
Accepted: 6 August 2018
First Online: 11 August 2018
Compliance with ethical standards
: The senior author is paid consultant for Zimmer (Warsaw, US), Adler Ortho (Milan, Italy) and CeramTec (Plochingen, Germany). The other authors declare that they have no conflict of interest.
: Ethical approval was not necessary as the registry collects personal data as standard practice and conceals the identity of the patients.