Abstract
Introduction
The Opera acetabular component (Smith & Nephew Ltd) shares many same design features with the Ogee (Depuy Int.). Differences are a malleable flange, instrumentation designed to improve cement pressurisation and the specifics of the UHMW-poly used.
Methods
Data was collected prospectively on 419 consecutive replacements (390 patients), performed between March 2000 and February 2005. A posterior approach was used, and the acetabulum was prepared with multiple key holes. Palacos-R bone cement containing Gentamicin was used with a cement pressuriser.
Results
There were 243 Operas (221 patients) and 176 Ogees (169 patients). There were 262 in female patients (62.5%) and age at surgery averaged 68.3yrs (25–92). Average follow-up of surviving patients was 185 months (165 – 225).
Acetabular abduction angle in both groups averaged 46° (25–65)
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Opera group: 27 (11.1%) acetabular components loosened aseptically, all associated with rapid wear. 16 (6.6%) acetabular components were revised (15 (6.2%) - aseptic loosening and 1 late infection. At 10 years 85% were graded Hodgkinson 0 or 1. Six femoral implants loosened (2.5%), 2 of which have been revised.
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Ogee group: 3 acetabular components (1.7%) were revised (2 - aseptic loosening (1.1%) and 1 for recurrent dislocation). None are currently loose. At 10 years 99% were graded Hodgkinson 0 or 1. There was no femoral loosening.
Conclusions
In the Opera group aseptic acetabular loosening (11.1% v 1.1%), acetabular revision for aseptic loosening (6.2 v 1.1%), aseptic femoral loosening (2.5% v 0) and Hodgkinson grading > 1 at 10 years (15% v 1%) were more common and associated with rapid wear. This must be attributable to poorer wear properties of the UHMW-poly of the Opera implant and patients with these components require regular surveillance to detect loosening.
