title: Chemically driven tetragonal-to-monoclinic polymorphic transformation in retrieved ZTA femoral heads from dual mobility hip implants.
abstract: Two short-term (two and nine months) retrieved zirconia-toughened alumina (ZTA) femoral heads and nine pristine femoral heads from the same manufacturer have been investigated with respect to their surface stability by means of confocal Raman spectroscopy. Quantitative estimations of monoclinic volume fraction have been carried out in both non-wear and main wear zones of the retrieved heads, which invariantly showed high volume fractions of monoclinic polymorph. In-depth (sub-surface) profiles, non-destructively collected in the main wear zones with the Raman probe in confocal configuration, indeed confirmed that polymorphic transformation was extended down to 100μm below the bearing surface of the femoral heads. Acceleration of tetragonal-to-monoclinic transformation rate leads to unexpectedly high fractions of monoclinic phase within very short-term in-vivo exposures. Phase transformation in-vivo is much more marked than what one could actually predict according to simply simulating a hydrothermal environment in-vitro and could not be simply ascribed to the mechanical stress fields generated during normal service at the bearing surface. Instead, the chemical consequences of metal contamination on the ZTA femoral head surface are shown to play the most detrimental role in phase destabilization.
authors.affiliation: Ceramic Physics Laboratory, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8585 Kyoto, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Boffelli
authors.affiliation: Ceramic Physics Laboratory, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8585 Kyoto, Japan; Materials Engineering and Applied Chemistry Department, University of Trieste, Via Valerio, 34127 Trieste, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Doimo
authors.affiliation: Ceramic Physics Laboratory, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8585 Kyoto, Japan.
authors.forename: E
authors.initials: E
authors.lastname: Marin
authors.affiliation: Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, Kamigyoku Hirokoji agaru, Kawaramachi-dori, 602-8566 Kyoto, Japan.
authors.forename: L
authors.initials: L
authors.lastname: Puppulin
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: W
authors.initials: W
authors.lastname: Zhu
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: N
authors.initials: N
authors.lastname: Sugano
authors.affiliation: Loma Linda University Medical Center, Department of Orthopaedics, 11406 Loma Linda Drive, Suite 606, Loma Linda, CA, USA.
authors.forename: I C
authors.initials: IC
authors.lastname: Clarke
authors.affiliation: Ceramic Physics Laboratory, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8585 Kyoto, Japan. Electronic address: pezzotti@kit.ac.jp.
authors.forename: G
authors.initials: G
authors.lastname: Pezzotti
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry*; D005270:Femur Head; D006622:Hip Prosthesis; D013059:Spectrum Analysis, Raman; D013314:Stress, Mechanical; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry*
chemical_list: D015040:Zirconium; D000537:Aluminum Oxide; C028541:zirconium oxide
keywords: Dual mobility hip implant; Metal contamination; Phase transformation; Raman spectroscopy; Zirconia-toughened alumina