Mid-term results of reconstruction rings used in combination with modular tantalum augments for Paprosky type III acetabular defects in revision hip arthroplasty.

Purpose: The combined use of reconstruction rings and modular trabecular metal (TM) augments can be a viable individual treatment in selected patients with large severe acetabular bone defects. However, clinical data on the outcome of this surgical technique is limited. This study aimed to evaluate mid-term results of reconstruction rings used in combination with modular TM augments for severe acetabular defects in revision hip arthroplasty. Methods: We retrospectively reviewed 23 patients with Paprosky type III A or B acetabular defects who underwent revision surgery using a reconstruction ring with a cemented cup in combination with a modular TM augment. 16 patients had type III A defects and 7 patients suffered from type III B defects. Clinical outcome was assessed using patient-reported outcome scores (PROMs). CT scans were used to assess preoperative bone loss and plain radiographs were used to determine postoperative implant migration. Blood tantalum concentrations were measured at latest follow-up and compared to a control group of patients without metal implants. Results: 18 patients could be contacted. 9 patients underwent a complete clinical and radiological follow-up examination as well as a blood test. The cumulative survival rate at 7.4 years with the endpoint 'acetabular component revision for any reason' was 86.7% (95% confidence interval 56%-96%). At the most recent follow-up two patients (9%) had undergone revision surgery due to aseptic loosening of the acetabular construct. Three patients showed radiological signs of loosening of the reconstruction ring without clinical symptoms. The PROMs improved significantly to the latest follow-up. Blood tantalum concentrations were elevated in the study group (0.06 µg/L) compared to controls (0.002 µg/L) (p < 0.001). Conclusions: In this study, favourable mid-term (mean 7.4 years) clinical and radiological outcomes of modular TM augments in combination with a reinforcement ring and cemented revision cups for individual reconstructing major acetabular defects were observed. Aseptic loosening is the main reason for revision, whereby the TM augment was firmly osseointegrated in all cases. Level of Evidence: Level IV, retrospective case series.