Retrieval study of commercially available knee implant coatings TiN, TiNbN and ZrN on TiAl6V4 and CoCr28Mo6 - Herbster, M; Döring, J; Nohava, J; Lohmann, C H; Halle, T; Bertrand, J (J Mech Behav Biomed Mater, 2020)