Long-Term Outcomes of Constrained Liners Cemented into Retained, Well-Fixed Acetabular Components

Background: Cementation of a constrained liner is a viable option for treating instability after total hip arthroplasty (THA) when the acetabular component is well fixed and well aligned. However, concerns regarding long-term mechanical failure and recurrent instability remain. The aim of this study was to evaluate the long-term survivorship, complications, and clinical and radiographic outcomes of constrained polyethylene liners cemented into well-fixed acetabular components at the time of revision THA. Methods: We identified 125 cases in which a constrained liner of 1 design was cemented into a retained, osseointegrated acetabular component during revision THA between 1998 and 2006. The mean patient age at revision was 70 years. Mean follow-up was 7 years. Survivorship data, risk of instability, and clinical and radiographic outcomes were analyzed. Results: Survivorship free from revision for instability was 86% at 5 years and 81% at 10 years. Survivorship free from aseptic acetabular component revision was 78% at 5 years and 65% at 10 years, with the most common failure mechanism being dissociation of the constrained liner from the acetabular component. Survivorship free from revision for any reason was 76% at 5 years and 60% at 10 years. The most common complications were instability and peri prosthetic joint infection, with cumulative incidences at 7 years of 18% and 11%, respectively. Harris hip scores did not significantly improve. Cup position did not affect implant survivorship or risk of dislocation. Conclusions: Cementing a constrained liner into a retained acetabular shell at the time of revision THA has durable longterm results, with 8 in 10 patients free from instability at 10 years. Aseptic acetabular survivorship was worse (65%) at 10 years, primarily due to dissociation of the constrained liner from the acetabular component.