Dual mobility for chronic hip instability: a solution option

A dual-mobility acetabular component consists of a large, fixed, porous-coated acetabular component and a bipolar femoral component. These components are often called tripolar components. This configuration provides a stable, well-fixed implant platform against bone and 2 articular interfaces, a large polyethylene surface directly apposed to the highly polished metal shell, and a standard sized (28 mm, 32 mm) femoral head captured within polyethylene. The dual-mobility cup was designed to reduce the incidence of dislocations in patients at increased risk of instability (eg, patients undergoing revision). The cup appears to offer a safe, effective, durable solution to hip instability. The concept has extensive laboratory and clinical support. Although the long-term durability of dual-mobility cups, particularly in young, active, large patients, is not known, the tested wear rates of the dual-mobility design with the current generation of highly cross-linked polyethylene are significantly lower than any previously reported wear rates. The recently released anatomic dual-mobility cup seeks to reduce the potential for iliopsoas impingement while retaining the stability and wear characteristics of the original dual-mobility design.