Pseudotumours, cobalt and clinical outcome in small head metal-on-metal versus conventional metal-on-polyethylene total hip arthroplasty

Hugo C van der Veen*, Inge Hf Reininga, Wierd P Zijlstra, Martijn F Boomsma, Sjoerd K Bulstra, Jos Jam van Raay

*Corresponding author for this work

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Background: Metal-on-metal total hip arthroplasty (MoM THA) is associated with the formation of pseudotumours. Studies mainly concern pseudotumour formation in large head MoM THA. We performed a long-term follow-up study, comparing pseudotumour incidence in small head metal-on-metal (SHMoM) THA with conventional metal-on-polyethylene (MoP) THA. Predisposing factors to pseudotumour formation were assessed. Methods: From a previous randomised controlled trial comparing SHMoM (28 mm) cemented THA with conventional MoP cemented THA, patients were screened using a standardised CT protocol for the presence of pseudotumours. Serum cobalt levels and functional outcome were assessed. Results: 56 patients (33 MoP and 23 MoM) were recruited after mean follow-up of 13.4 years (SD 0.5). The incidence of pseudotumours was 1 (5%) in the SHMoM THA cohort and 3 (9%) in the MoP THA cohort. Prosthesis survival was 96% for both SHMoM and MoP THAs. Serum cobalt levels did not exceed acceptable clinical values (<5 µg/L) whereas no differences in cobalt levels were detected at follow-up between both groups. Oxford and Harris Hip Scores were good and did not differ between SHMoM and MoP THA. Conclusions: This long-term follow-up study shows a low incidence of pseudotumour formation and good functional outcome in cemented head-taper matched SHMoM and MoP THA.

Original languageEnglish
Pages (from-to)56-63
Number of pages8
JournalHip international
Issue number1
Early online date2019
Publication statusPublished - Jan-2020


  • Cobalt
  • metal-on-metal
  • pseudotumour
  • small head
  • total hip arthroplasty
  • AGE

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