Revision total hip arthroplasty (rTHA) for major acetabular bone loss is technically demanding due to challenges in achieving stable fixation, restoring hip biomechanics, and ensuring long-term osseointegration. Modular porous acetabular systems offer intraoperative adaptability, multipoint fixation, and enhanced biological integration, yet comparative mid-term outcomes in heterogeneous Paprosky II–III defects remain limited.

We conducted a retrospective comparative study of 80 patients undergoing rTHR for Paprosky II–III acetabular defects between 2017 and 2021 at a tertiary referral center. Forty patients received one modular cementless acetabular reconstruction system (Group A) and 40 received another modular cementless cup–cage system (Group B). Implant selection was based on surgeon preference and implant availability; no pelvic discontinuities were included. Preoperative evaluation included clinical assessment, radiographs, and CT-based Paprosky classification. Surgical techniques, implant positioning, and postoperative rehabilitation were standardized. Primary outcomes were functional recovery (Merle d’Aubigné–Postel score) and radiographic stability; secondary outcomes included operative metrics and complications. Follow-up ranged from 48 to 60 months, with mean follow-up of 52 months in Group A and 50 months in Group B.

Both groups were demographically comparable. Group B demonstrated significantly longer operative times (175 ± 45 vs 150 ± 41 min) and greater intraoperative blood loss (942 ± 262 vs 781 ± 218 mL; p < 0.01). Radiographic evaluation showed stable cup fixation in all patients, minimal non-progressive radiolucent lines, and complete osseointegration. Functional scores improved significantly in both groups, with no intergroup difference at final follow-up (Group A: 8.4 ± 1.6 → 15.8 ± 1.9; Group B: 8.1 ± 1.7 → 16.1 ± 1.7; p = 0.42). Complications were few and comparable: superficial infection 1/40 (2.5%) vs 1/40 (2.5%), deep infection 1/40 (2.5%) vs 1/40 (2.5%), intraoperative blood loss >1500 mL 0/40 (0%) vs 2/40 (5%), no dislocations or periprosthetic fractures. Re-revision-free survival at 48 months was 97.5% in both cohorts (p = 0.94). Differences in operative time and blood loss were related to defect complexity and the need for additional augments rather than to the implant category itself.

Both modular acetabular systems provide reliable mid-term outcomes in complex acetabular rTHA, achieving substantial functional improvement, stable fixation, low complication rates and comparable functional and radiological outcomes. These findings support the use of either system for managing complex acetabular defects, with implant selection guided by intraoperative requirements, defect morphology, and surgeon experience.

III; Retrospective comparative cohort study.