Complete Dissociation of the Polyethylene Component in a Newly Available Dual-Mobility Bearing Used in Total Hip Arthroplasty: A Case Report.

Abstract

Bousquet developed the concept of the dual-mobility bearing in total hip arthroplasty1,2. The design allows for two articulations between the femoral head and the acetabular component. The polyethylene component widens the effective diameter of the femoral head with the goal of increasing stability2. In the literature, there have been reports that dual-mobility bearings used in patients undergoing primary total hip arthroplasty lead to decreased dislocation rates1,3-6. Some have also described the use of dual-mobility bearings in revision total hip arthroplasty for patients experiencing recurrent dislocation7-9. Dual-mobility bearings have been used since the 1970s in Europe, and several studies have reported long-term results; however, only the more recent studies are available in the English-language literature1,4,5. In these studies, intraprosthetic dislocation is described as a specific complication in dual-mobility bearings in which the intervening polyethylene component has dissociated from the femoral head1,5,6. Intraprosthetic dislocation occurs because of excessive wear over time between the femoral head-neck junction and the retentive barrier of the polyethylene component. This excessive wear can occur because of the design and material of the femoral head and neck, the formation of periprosthetic fibrosis, and/or the stress applied to the components by more active patients1,2. In the European literature, Stigbrand and Ullmark recently reported three cases of complete dissociation of the polyethylene component of dual-mobility bearings used in total hip arthroplasties after closed reduction10. All three cases occurred within seven months of implantation, before the onset of wear. We present a patient who was found to have a polyethylene component completely dissociated from the femoral head of a dual-mobility bearing used in total hip arthroplasty after …