Unstable Total Hip Arthroplasty: Should It Be Revised Using Dual Mobility Implants? A Retrospective Analysis from the R.I.P.O. Registry

Total hip arthroplasty (THA) is one of the most common surgical procedures in orthopedics; however, it is subjected to different kinds of failures, one of them being dislocation. Many different prosthetic designs have been developed to overcome this problem, such as dual mobility coupling. The main purpose of this article is to determine whether there are differences regarding the revision surgery of unstable THA comparing the risk of failure between dual mobility cup (DMC) implants, standard implants, and among different head sizes. A registry-based population study has been conducted by analyzing data collected by the Emilia Romagna Registry of Orthopedic Prosthetic Implants (RIPO), including a total of 253 implants failed for dislocation and instability that were operated on by cup revision surgery between 2000 and 2019. The selected population has been divided into two groups based on the insert type: standard and DMC. The age at revision surgery was significantly lower in the standard cup group with respect to DMC (p = 0.014 t-test), with an average age of 71.2 years (33–96 years range) for the standard cups and 74.8 years (48–92 years range) for the DMC group. The cumulative survival of DMC implants was 82.0% at 5-years, decreasing to 77.5% at a 10-year follow-up, which is not significantly different from standard cups (p = 0.676, Log-Rank test). DMC implants showed a significantly lower risk of re-revision for dislocation compared to standard cups (p = 0.049). Femoral heads ≥36 mm had a higher overall survival compared to smaller femoral heads (p = 0.030). This study demonstrated that DMC or femoral heads ≥36 mm are a valid choice to manage THA instability and to reduce the revision rate for dislocation at a mid-term follow-up; in those selected and targeted patients, these options should be taken into consideration because they are associated with better outcomes.