Midterm Outcomes of Revision Total Hip Arthroplasty With Cementation of a Monoblock Dual-Mobility Bearing Cup in a Porous Revision Acetabular Shell.

BACKGROUND: Dual-mobility (DM) articulations and porous acetabular shells are increasingly used to address instability and mechanical loosening in revision total hip arthroplasty (rTHA). However, reports of longer-term outcomes with the new generation of DM articulations and porous shells remain limited. Our study reports the use and outcomes of a cemented monoblock DM cup in a fully porous acetabular shell in complex rTHA cases with midterm follow-up. METHODS: A retrospective study was conducted of rTHAs with an acetabular construct of a monoblock DM cup cemented into a fully porous acetabular shell between June 2016 and December 2019. Baseline demographics, operative information, and outcomes were gathered for a total of 55 patients. Ten patients died, and 4 were lost to follow-up at 5 years; 41 patients were included in the analysis of midterm outcomes. RESULTS: The most common indications for rTHA were acetabular component loosening (43.6%), periprosthetic joint infection (PJI) (16.4%), dislocation (12.7%), and periprosthetic fracture (9.1%). Preoperative acetabular bone loss assessment found 43.7% type IIA, 9.1% IIB, 20.0% IIC, 23.6% IIIA, and 3.6% IIIB according to the Paprosky classification. Six patients (10.9%) were readmitted within 90 days for PJI (n = 5; 9.1%) or dislocation (n = 1; 1.8%). Four patients (9.8%) required revision of the construct: 2 for PJI, 1 case of instability, and 1 case of aseptic loosening of the acetabular component with significant acetabular bone loss. The average time to revision was 1.4 years (range, 0.1-3.8 years). The mean follow-up period was 6.4 years (range, 4.7-8.2 years). The cup in cup construct had an all-cause survivorship of 95.8% and 90.0% at 1 and 5 years, respectively, and aseptic survivorship rates of 97.9% and 94.7% at 1 and 5 years, respectively. CONCLUSIONS: This cohort of 55 patients who underwent complex rTHA with a monoblock DM cup cemented into a porous acetabular shell exhibited reliable fixation and low revision rates. In complex revision cases where instability and inadequate fixation are concerns, these outcomes support continued consideration and use of this unique and durable construct.