The purpose of this study was to evaluate the medium-term survival of a dual mobility (D.M.) new generation cup: Polarcup® (Smith&Nephew, Fort Worth, Texas) in primary hip arthroplasty, in a population over the age of 70 (mean in our study: 80 years old). In comparison with other studies, our results are similar in terms of medium-term implant survival (100% after 9 years of follow-up, with the occurrence of nine periprosthetic femur fractures long after the operation). This type of cup is indicated for patients with a high risk of dislocation, aged between 70 and 75 years old, with neurological pathologies, alcoholism, low muscle trophicity and prosthesis revision, as well as tumor pathology requiring cementing of the cup in a Kerboull cross-type reconstruction ring. Wear problems occurred at the beginning of the first-generation DM cups use because the surface condition and the geometry of the prosthetic neck are involved in these wear phenomena. This led to the current preference for stems with smooth necks without extraction notches and highly cross-linked polyethylene. Currently, despite a wear and survival rate comparable to that of fixed polyethylene, the risk of intra-prosthetic dislocation (2%) specific to this type of implant should make their use cautious, especially in young and active patients (1). A more widespread use in patients over 70 years of age, supported by the significant reduction in the dislocation risk, as well as the very favorable medium-term survival results of new generation D.M. implants demonstrated by the Australian 2021 registry, could lead to a significant economic advantage (2).
What is already known about the topic?
The new generation of D.M. cups using highly cross-linked polyethylene, including the Polarcup® cup (Smith&Nephew, Fort Worth, Texas), coupled with the use of a smooth-necked femoral stem, have a longer life span than older generation D.M. cups.
What does this article bring up for us?
The encouraging results regarding medium-term longevity, as reported in the Australian 2021 registry (fig. 6 and 7), and the significant reduction of the dislocation risk (fig. 8) could lead to a more widespread use of the new generation D.M. cup in primary hip arthroplasty in people over 70 years of age, resulting in health care savings.
Key Words
Hip arthroplasty, dual mobility, survival rate, economic advantage