Two-stage exchange of infected total hip arthroplasty with a dual-mobility cup is associated with a low instability rate.

Introduction: The two-stage management of hip Prosthetic Joint Infection (PJI) is faced with a high rate of dislocation. Dual mobility (DM) cups have proved effective in reducing the risk of dislocation, but few data are available on the two-stage management of hip PJI. The objectives of this retrospective cohort study were to analyze the rate of dislocation, and the rate of recurrent dislocation and to identify risk factors for dislocation. Our hypothesis was that the use of a DM cup during a two-stage replacement had a low instability rate.

Methods: Data from 70 two-stage changes with DM cup reimplantation performed in our centre between 2011 and 2020 were retrospectively collated. The mean age was 69 years [18-93], with a mean follow-up of 3.4 years [1.5-9.6]. Dislocation rates and risk factors for prosthetic instability were collected. Univariate and multivariate analyses were performed to identify risk factors favouring prosthetic instability.

Results: The rate of dislocation at the last follow-up was 8.6% (6/70), including 4.3% (3/70) in patients with no infection recurrence. The rate of recurrent dislocation was 0% when infection was controlled. The occurrence of spacer dislocation, the presence of immunosuppressive and antiaggregant medication, the local grade of the McPherson score and infection treatment failure were associated with the occurrence of a dislocation. No risk factors were identified in the multivariate analysis.

Discussion: Compared with the rates reported in the literature, the use of a DM cup seems indicated in this context in order to lower the risk of recurrent dislocation. Preventing spacer dislocation and infection recurrence seems to be essential to avoid the risk of instability of the future prosthetic hip.