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· DOS Abstracts
High frequency of cystic pseudotumors in large-
head metal-on-metal total hip arthroplasty at 5-7
years follow-up.
Mette Holm Hjorth , Niels Egund, Inger Mechlenburg, Stig Storgaard Jakobsen,
Kjeld Søballe, Maiken Stilling
Department of Orthopaedics , Aarhus University Hospital ; Department of
Radiology, Aarhus University Hospital
Background:
Large-head metal-on-metal (MoM) total hip arthroplasty (THA)
has been associated with pseudotumor formation and high revision rates.
Purpose / Aim of Study:
To investigate the frequency of pseudotumors,
metal-ion concentrations and radiographic and clinical outcome in patients with
MoM THA.
Materials andMethods:
A consecutively included series of 41 patients/49hips
(31 males) with a mean age of 52 (28-68) years, participated in a 5-7- year
follow-up study of their large-headMoM THA (M2a Magnum, Biomet). Patients
were evaluated with magnetic resonance imaging (MRI), serum metal-ion con-
centrations, conventional radiographs, and clinical outcome measures of Harris
Hip Score (HHS) and Oxford Hip Score (OHS).
Findings / Results:
18 of 47 hips (38%) had MRI-verified pseudotumors, all
cystic, with a mean dimension of 1.1 x 2.6 x 0.4 cm. Acetabular cup anteversion
was mean 28+5° in patients with a pseudotumor and mean 24 +7° in patients
without a pseudotumor (p=0.009). Serum metal-ion concentrations, acetabu-
lar cup inclination and clinical outcome measures of HHS and OHS were similar
between patients with and without a pseudotumor.
Conclusions:
At 5-7 year after surgery, MRI-verified cystic pseudotumors
were frequently observed in large-head MoM THA, without relation to clinical
symptoms and metal-ion concentrations but with relation to cup- anteversion.
The clinical relevance and the natural history of cystic pseudotumors in asymp-
tomatic patients remain unknown; hence, we will continue to monitor these pa-
tients regularly.
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