Abstract
While total hip arthroplasty (THA) is the most predictable and successful operation for relieving pain and restoring function in the arthritic hip, instability and dislocation have been identified as the most common cause (22.5%) of revision THA in the United States. Thus, minimizing the complications of impingement and dislocation are major goals for surgeons and implant designers.
A dual-mobility (DM) socket design, where there is an additional bearing with a mobile polyethylene component between the prosthetic head and the acetabular shell, was introduced in the United States in 2010. Developed by Bousquet in 1974, the DM design has been shown to be a durable solution to hip instability after THA. The smaller inside diameter head offers the potential advantage of lower wear and the larger outside diameter head offers the potential advantage of improved stability. A review of eight studies using a DM design noted only two dislocations in 1,386 (0.1%) primary THAs. Initially, indications were advocated for patients with increased instability risk as in revision THA or THA after femoral neck fracture. However, with larger diameter metal-on-metal articulations falling out of favor, DM components are increasingly being used in younger patients.
Between 2011 and 2014, the author has used DM sockets in over 400 primary THAs (age, 22–92 years). Only one dislocation was noted in this group (femoral neck fracture). One loose cup was revised. Dislocation of the smaller femoral head from the larger polyethylene head remains a theoretical risk with DM designs.
