title: Pseudotumour incidence, cobalt levels and clinical outcome after large head metal-on-metal and conventional metal-on-polyethylene total hip arthroplasty: mid-term results of a randomised controlled trial.
abstract: We compared the incidence of pseudotumours after large head metal-on-metal (MoM) total hip arthroplasty (THA) with that after conventional metal-on-polyethylene (MoP) THA and assessed the predisposing factors to pseudotumour formation. From a previous randomised controlled trial which compared large head (38 mm to 60 mm) cementless MoM THA with conventional head (28 mm) cementless MoP THA, 93 patients (96 THAs: 41 MoM (21 males, 20 females, mean age of 64 years, standard deviation (sd) 4) and 55 MoP (25 males, 30 females, mean age of 65 years, sd 5) were recruited after a mean follow-up of 50 months (36 to 64). The incidence of pseudotumours, measured using a standardised CT protocol was 22 (53.7%) after MoM THA and 12 (21.8%) after MoP THA. Women with a MoM THA were more likely to develop a pseudotumour than those with a MoP THA (15 vs 7, odds ratio (OR) = 13.4, p < 0.001). There was a similar incidence of pseudotumours in men with MoM THAs and those with MoP THAs (7 vs 5, OR = 2.1, p = 0.30). Elevated cobalt levels (≥ 5 microgram/L) were only associated with pseudotumours in women with a MoM THA. There was no difference in mean Oxford and Harris hip scores between patients with a pseudotumour and those without. Contrary to popular belief, pseudotumours occur frequently around MoP THAs. Women with a MoM THA and an elevated cobalt level are at greatest risk. In this study, pseudotumours had no effect on the functional outcome after either large head MoM or conventional MoP THA.
authors.affiliation: University of Groningen, University Medical Center Groningen, P.O. Box 30.033, 9700 RM Groningen, The Netherlands.
authors.forename: H C
authors.initials: HC
authors.lastname: van der Veen
authors.affiliation: University of Groningen, University Medical Center Groningen, P.O. Box 30.033, 9700 RM Groningen, The Netherlands.
authors.forename: I H F
authors.initials: IH
authors.lastname: Reininga
authors.affiliation: Medical Center Leeuwarden, P.O. Box 888, 8901 BR Leeuwarden, The Netherlands.
authors.forename: W P
authors.initials: WP
authors.lastname: Zijlstra
authors.affiliation: Isala Hospital, P.O. Box 10.400, 8000 GK Zwolle, The Netherlands.
authors.forename: M F
authors.initials: MF
authors.lastname: Boomsma
authors.affiliation: University of Groningen, University Medical Center Groningen, P.O. Box 30.001, 9700 RB Groningen, The Netherlands.
authors.forename: S K
authors.initials: SK
authors.lastname: Bulstra
authors.affiliation: Martini Hospital, P.O. Box 30.033, 9700 RM Groningen, The Netherlands.
authors.forename: J J A M
authors.initials: JJ
authors.lastname: van Raay
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D003035:Cobalt / Q000097:blood*; D005260:Female; D005500:Follow-Up Studies; D006104:Granuloma, Plasma Cell / Q000097:blood / Q000000981:diagnostic imaging / Q000209:etiology*; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008670:Metals; D008875:Middle Aged; D020959:Polyethylene; D011474:Prosthesis Design; D011475:Prosthesis Failure; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D008670:Metals; D003035:Cobalt; D020959:Polyethylene
keywords: Metal-on-metal; Metal-on-polyethylene; cobalt; pseudotumour; total hip arthroplasty