Acetabular Liner Dissociation: A Comparative Study of Two Contemporary Uncemented Acetabular Components
Background There are a number of reports of polyethylene liner dissociation of third generation modular acetabular components. This study compares our experience with 2 contemporary systems to determine whether this is an implant or class specific problem. Methods This is a single center retrospective study of 961 primary total hip arthroplasties using 2 third generation modular cementless acetabular shells: Pinnacle (535) and R3 (426) with a polyethylene liner. Details of all revisions were obtained from local databases and the New Zealand Joint Registry. Kaplan Meier survival curves were calculated for all cause revision, acetabular reoperation (including liner exchange) and liner dissociation. Results There were 17 revisions in group 1 (Pinnacle; DePuy Synthes) 17 for recurrent dislocation, 6 for liner dissociations (1.12% 3 for femoral loosening, and one for deep infection. In group 2 (R3; Smith and Nephew) there were 4 revision procedures: one for infection, 2 for dislocation, and one femoral revision for periprosthetic fracture. There were significantly higher proportions revised in group 1 for all cause revision, acetabular reoperation, and dissociation (P .024 to 0.038) The 7 year survival for all cause revision was 96.1% for Pinnacle and 99.0% for R3 (P .022) and that in the acetabular reoperation group was 96.9% for Pinnacle and 99.3% for R3 (P .035) Conclusions There was a higher revision rate for the Pinnacle acetabular component than for the R3 at 7 years. This was mainly due to polyethylene liner dissociation that can occur early or late. It appears to be a problem specific to the Pinnacle cup design rather than a feature of similar third generation acetabular components.
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