title: Reconciling in vivo and in vitro kinetics of the polymorphic transformation in zirconia-toughened alumina for hip joints: I. Phenomenology.
abstract: Exploitation of the toughening effect induced by polymorphic phase transformation of zirconia in zirconia-toughened alumina (ZTA) requires the composite being properly designed and carefully manufactured. A sound algorithm for predicting phase stability along with strict control over manufacturing steps are required in order to prevent possible in vivo surface degradation or implant fracture. This paper is the first in a series of three monographs, which aim at: (i) statistically comparing the in vitro/in vivo phenomenology of surface-metastability for currently marketed ZTA femoral heads; (ii) refining pre-existing theoretical models for predicting in vivo zirconia phase metastability via the use of accelerated in vitro ageing experiments; and, (iii) providing a rationale for the mechanism(s) involved with the observed in vivo surface metastability. This initial paper of a series of three, which specifically deals with item (i), shows discrepancies between the levels of polymorphic phase transformation detected in ZTA retrievals and in vitro predictions, and attempts a phenomenological analysis of the reasons behind such discrepancies. Moreover, marked inhomogeneities are also found among as-manufactured components through different years of production. The phenomenology of retrievals' data suggests key roles for both the presence of metallic stain and the initial value of monoclinic volume fraction.
authors.affiliation: Department of Orthopaedic Surgery, University of Missouri, Columbia, MO 65212, United States; Amedica Corporation, 1885 West 2100 South, Salt Lake City, UT 84119, United States. Electronic address: BalB@health.missouri.edu.
authors.forename: B Sonny
authors.initials: BS
authors.lastname: Bal
authors.affiliation: Department of Medical Engineering for Treatment of Bone and Joint Disorders, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0854, Japan.
authors.forename: Wenliang
authors.initials: W
authors.lastname: Zhu
authors.affiliation: Ceramic Physics Laboratory, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8126 Kyoto, Japan.
authors.forename: Matteo
authors.initials: M
authors.lastname: Zanocco
authors.affiliation: Ceramic Physics Laboratory, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8126 Kyoto, Japan.
authors.forename: Elia
authors.initials: E
authors.lastname: Marin
authors.affiliation: Department of Medical Engineering for Treatment of Bone and Joint Disorders, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0854, Japan.
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Sugano
authors.affiliation: Amedica Corporation, 1885 West 2100 South, Salt Lake City, UT 84119, United States.
authors.forename: Bryan J
authors.initials: BJ
authors.lastname: McEntire
authors.affiliation: Ceramic Physics Laboratory, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8126 Kyoto, Japan.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Pezzotti
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry*; D019644:Arthroplasty, Replacement, Hip; D001672:Biocompatible Materials / Q000737:chemistry* / Q000627:therapeutic use; D005270:Femur Head / Q000737:chemistry; D050723:Fractures, Bone / Q000628:therapy; D006622:Hip Prosthesis; D006801:Humans; D007700:Kinetics; D018613:Microscopy, Confocal; D011474:Prosthesis Design; D013059:Spectrum Analysis, Raman; D015040:Zirconium / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D015040:Zirconium; D000537:Aluminum Oxide; C028541:zirconium oxide
keywords: Femoral heads; Hip arthroplasty; Metal stain; Polymorphic phase transformation; Zirconia-toughened alumina