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Retrospective cohort study of the performance of the Pinnacle metal on metal (MoM) total hip replacement: a single-centre investigation in combination with the findings of a national retrieval centre
  1. David John Langton1,
  2. Raghavendra Prasad Sidaginamale1,
  3. Peter Avery2,
  4. Sue Waller3,
  5. Ghanshyabhai Tank1,
  6. James Lord4,
  7. Thomas Joyce2,
  8. Nick Cooke1,
  9. Raj Logishetty1,
  10. Antoni Viraf Francis Nargol1
  1. 1University Hospital of North Tees, Stockton, UK
  2. 2Newcastle University, Newcastle upon Tyne, Newcastle, UK
  3. 3North Tees Nuffield Hospital, Stockton, UK
  4. 4Virginia Tech, Blacksburg, Virginia, USA
  1. Correspondence to David John Langton; djlangton22{at}yahoo.com

Abstract

Objectives To determine risk factors for revision in patients implanted with a commonly used metal on metal (MoM) hip replacement.

Design Retrospective cohort study in combination with a prospective national retrieval study (Northern Retrieval Registry (NRR)).

Setting Combined orthopaedic unit in combination with the NRR.

Participants All patients implanted with a DePuy Pinnacle MoM hip prostheses by the 2 senior authors were invited to attend for a review which included clinical examination, blood metal ion measurements, radiographs and targeted imaging. Explanted components underwent wear analysis using validated methodology and these results were compared with those obtained from the NRR.

Results 489 MoM Pinnacle hips were implanted into 434 patients (243 females and 191 males). Of these, 352 patients attended the MoM recall clinics. 64 patients had died during the study period. For the purposes of survival analysis, non-attendees were assumed to have well-functioning prostheses. The mean follow-up of the cohort as a whole was 89 months. 71 hips were revised. Prosthetic survival for the whole cohort was 83.6% (79.9–87.3) at 9 years. The majority of explanted devices exhibited signs of taper junction failure. Risk factors for revision were bilateral MoM prostheses, smaller Pinnacle liners, and implantation in 2006 and later years. A significant number of devices were found to be manufactured out of their specifications. This was confirmed with analysis of the wider data set from the NRR.

Conclusions This device was found to have an unacceptably high revision rate. Bilateral prostheses, those implanted into female patients and devices implanted in later years were found to be at greater risk. A significant number of explanted components were found to be manufactured with bearing diameters outside of the manufacturer's stated tolerances. Our findings highlight the clinical importance of hitherto unrecognised variations in device production.

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

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