Abstract
A conceptually new acetabular design is currently available when performing a total hip arthroplasty – the dual mobility socket. Essentially this is a press-fit acetabular component with a polished surface that articulates with a large polyethylene head with a 28 mm ball inserted into that polyethylene in a similar fashion to a bipolar design.
Proponents of this design advocate its use to reduce the risk of dislocation, and it is being offered as an alternative to constrained liners and also as a potential prophylactic application in revision and high risk patients.
The concerns regarding this construct include:
- 1.
Wear
A large polyethylene head articulating against a polished metal surface will have much greater wear than a conventional metal against poly bearing. Hip simulator data has shown this previously. To demonstrate a reduction in wear, one must compare unlike polyethylenes, or extremes in component positioning.
- 2.
Clinical data
At present there are only 2 published reports on this implant, both from the same centre. These are both short-term follow up reports (min 2 year follow up). There are no control groups with other implants in these same “at risk” patients. There is no registry data to date on this implant.
- 3.
Patient Population
A difficult question to answer is which patient is at risk for dislocation and if one was going to apply this new technology, which patient would receive it. In the original published series, 26% of patients undergoing THA had this implant. Does the increased risk of wear and osteolysis warrant the use of this implant in a primary setting? In a revision setting, the implant available in North America has no provision for any screw fixation – is that practical in these challenging cases?
There are many options available to both manage and to prevent hip instability. Any new implant must show equivalence to current devices on the many fronts of wear, fixation, midterm results, complications and costs.
