title: Environmental Stability and Residual Stresses in Zirconia Femoral Head for Total Hip Arthroplasty: In Vitro Aging versus Retrieval Studies.
abstract: The objective of this study was to compare the low temperature degradation (LTD) behavior of femoral heads made of 3Y-TZP as observed on retrievals with that induced in vitro upon prolonged exposures to a hydrothermal environment. The time-dependent evolution of tetragonal-to-monoclinic transformation and the related residual stresses were nondestructively monitored by Raman microspectroscopy. An increasing intensification of tensile and compressive stresses was detected with increasing hydrothermal aging duration in tetragonal and monoclinic phases, respectively. The dependence of monoclinic fraction upon exposure time was rationalized through the Mehl-Avrami-Johnson (MAJ) formalism in order to interpret the LTD process according to a two-step mechanism of formation and growth of monoclinic nuclei. In vitro results were compared to in vivo monoclinic contents in the same type of 3Y-TZP head retrievals after implantation periods of 1.6-16.6 y, also including literature data previously reported by other authors. One-hour exposure under the selected aging condition is estimated to correspond to in vivo exposures of 4 and 2 years according to ISO and ASTM criteria, respectively. A critical review of these two criteria according to the present analyses revealed that the ASTM simulation predicts more closely the in vivo results as compared to the ISO one.
authors.affiliation: Department of Orthopaedic Surgery, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Arita
authors.affiliation: Department of Orthopaedic Surgery, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan ; Department of Bone and Joint Biomaterial Research, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan.
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Takahashi
authors.affiliation: Ceramic Physics Laboratory, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, Kyoto 606-8585, Japan.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Pezzotti
authors.affiliation: Department of Orthopaedic Surgery, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Shishido
authors.affiliation: Department of Orthopaedic Surgery, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan.
authors.forename: Toshinori
authors.initials: T
authors.lastname: Masaoka
authors.affiliation: Department of Orthopaedic Surgery, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Sano
authors.affiliation: Department of Orthopaedic Surgery, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan.
authors.forename: Kengo
authors.initials: K
authors.lastname: Yamamoto
mesh_terms: D019644:Arthroplasty, Replacement, Hip; D005270:Femur Head / Q000473:pathology / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D008422:Materials Testing; D011475:Prosthesis Failure; D013499:Surface Properties; D013696:Temperature; D015040:Zirconium / Q000737:chemistry* / Q000627:therapeutic use
chemical_list: D015040:Zirconium; C028541:zirconium oxide