title: The relation between titanium taper corrosion and cobalt-chromium bearing wear in large-head metal-on-metal total hip prostheses: a retrieval study.
abstract: BACKGROUND
  Revision of hip implants due to adverse tissue reactions to metal debris has been associated with wear and corrosion of the metal-on-metal bearing articulation and the modular taper interface. Bearing articulation wear is increased in conditions of poor lubrication, which can also lead to high friction moments that may cause corrosion at the taper interface. This suggests that wear of the bearing and increased corrosion of the taper interface should occur simultaneously, which was investigated in this study.
  
  
  METHODS
  Forty-three large-diameter cobalt-chromium bearings of the same design, implanted with a titanium stem using a titanium adapter, were retrieved at revision at a single center. Retrievals were grouped according to visual inspection of the female taper surface of the adapter into slight and severe corrosion groups. Volume change of bearing and taper surfaces was assessed using a coordinate measurement machine. Serum ion concentrations were determined for forty-three patients, whereas tissue metal concentration was measured for twelve patients.
  
  
  RESULTS
  Severe taper corrosion was observed in 30% of the retrievals. Corrosion was observed either as material deposition or wear. The overall bearing wear rate was significantly higher in the group with severe taper corrosion than in the group with slight corrosion (7.2 ± 9.0 mm(3)/yr versus 3.1 ± 6.8 mm(3)/yr, respectively; p = 0.023) as were the serum cobalt (40.5 ± 44.9 μg/L versus 15.2 ± 23.9 μg/L, respectively; p = 0.024) and chromium ion concentrations (32.7 ± 32.7 μg/L versus 12.0 ± 15.1 μg/L, respectively; p = 0.019). Serum metal ion concentrations were more consistent indicators of wear than tissue metal concentrations.
  
  
  CONCLUSIONS
  The increased bearing articulation wear and serum metal ion concentrations in cases with taper interface corrosion support the hypothesis that increased friction in the joint articulation is one of the factors responsible for simultaneous articulation and taper damage. However, independent taper or bearing damage was also observed, suggesting that other factors are involved in the process.
authors.affiliation: Biomechanics Section, TUHH Hamburg University of Technology, Denickestraße 15, 21073 Hamburg, Germany. E-mail address for F. Witt: witt@tuhh.de. E-mail address for N.E. Bishop: bishop@tuhh.de. E-mail address for M.M. Morlock: morlock@tuhh.de.
authors.forename: F
authors.initials: F
authors.lastname: Witt
authors.affiliation: Department of Orthopedic Surgery, Isala Clinics, P.O. Box 10400, 8000 GK, Zwolle, The Netherlands. E-mail address for B.H. Bosker: b.h.bosker@isala.nl. E-mail address for H.B. Ettema: h.b.ettema@isala.nl. E-mail address for C.C.P.M. Verheyen: C.C.P.M.Verheyen@isala.nl.
authors.forename: B H
authors.initials: BH
authors.lastname: Bosker
authors.affiliation: Biomechanics Section, TUHH Hamburg University of Technology, Denickestraße 15, 21073 Hamburg, Germany. E-mail address for F. Witt: witt@tuhh.de. E-mail address for N.E. Bishop: bishop@tuhh.de. E-mail address for M.M. Morlock: morlock@tuhh.de.
authors.forename: N E
authors.initials: NE
authors.lastname: Bishop
authors.affiliation: Department of Orthopedic Surgery, Isala Clinics, P.O. Box 10400, 8000 GK, Zwolle, The Netherlands. E-mail address for B.H. Bosker: b.h.bosker@isala.nl. E-mail address for H.B. Ettema: h.b.ettema@isala.nl. E-mail address for C.C.P.M. Verheyen: C.C.P.M.Verheyen@isala.nl.
authors.forename: H B
authors.initials: HB
authors.lastname: Ettema
authors.affiliation: Department of Orthopedic Surgery, Isala Clinics, P.O. Box 10400, 8000 GK, Zwolle, The Netherlands. E-mail address for B.H. Bosker: b.h.bosker@isala.nl. E-mail address for H.B. Ettema: h.b.ettema@isala.nl. E-mail address for C.C.P.M. Verheyen: C.C.P.M.Verheyen@isala.nl.
authors.forename: C C P M
authors.initials: CC
authors.lastname: Verheyen
authors.affiliation: Biomechanics Section, TUHH Hamburg University of Technology, Denickestraße 15, 21073 Hamburg, Germany. E-mail address for F. Witt: witt@tuhh.de. E-mail address for N.E. Bishop: bishop@tuhh.de. E-mail address for M.M. Morlock: morlock@tuhh.de.
authors.forename: M M
authors.initials: MM
authors.lastname: Morlock
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation; D002857:Chromium / Q000737:chemistry / Q000627:therapeutic use; D003035:Cobalt / Q000737:chemistry / Q000627:therapeutic use; D003343:Corrosion; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D061825:Metal-on-Metal Joint Prostheses; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012042:Registries; D014025:Titanium / Q000737:chemistry / Q000627:therapeutic use
chemical_list: D002857:Chromium; D003035:Cobalt; D014025:Titanium