Massive wear and metallosis of an Acetabular Cup System presenting as pseudodislocation

In primary and revision total hip arthroplasty (THA), the acetabular component continues to pose greater challenges than the femoral component. Numerous factors lead to polyethylene wear, which subsequently affects primary THA survival. Progressive polyethylene wear is associated with the occurrence of osteolysis, especially overlying the acetabulum, which can lead to component loosening and subsequent revision. Polyethylene failure usually manifests as massive liner wear up to the metal shell, fracture of the liner, or a combination of both. There is often a small amount of metallosis associated with this pathology. To our knowledge, massive wear of the acetabular metal shell, however, has not previously been reported in the literature. This article describes a case of massive wear through a polyethylene liner and the acetabular metal shell of an Acetabular Cup System (DePuy, Leeds, United Kingdom) that presented as an apparent dislocation 13 years following the index operation. The pseudodislocation was intraoperatively found to be penetration of the femoral head through the acetabular shell. The acetabular component was consequently revised to a larger cementless cup. The femoral component was mechanically stable and required no revision. Patients with long-standing Acetabular Cup System THA may experience acetabular metal shell wear-through phenomena presenting as a pseudodislocation, and this possibility should be taken into consideration during preoperative planning.