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Ankle arthroplasty is a viable treatment option for end-stage ankle arthritis and has shown improvements in pain relief, motion, as well as function and gait. Newer generation total ankle prostheses have improved instrumentation and surgical techniques, as well as minimal bone resection on both the tibia and talus. The purpose of this systematic review was to determine the short-term clinical success of the INFINITY total ankle, including the common complications and rate of revision with this prosthesis. We performed a systematic review of electronic databases that included reported complications and revisions using this prosthesis. Complications were recorded according to the Glazebrook classification. Six total published studies with clinical outcomes and complications and 432 prostheses were included. The weighted mean follow-up was 24.5 months and weighted mean patient age was 62.3 years. There were 43 (10.0%) total complications—9 low grade, 16 medium grade, and 18 high grade. There were 26 total revision procedures (6.0%). Revisions were mostly performed for deep infection, aseptic loosening, and subsidence. When including deep infections, the overall implant survivorship was 94%. When excluding the 8 deep infections requiring revision, implant survivorship was 96%. The INFINITY has acceptable short-term complication and revision rates. This fourth-generation prosthesis compares to prior reported studies with earlier generation ankle implants in the short term. Level of Evidence: IV

Heterotopic ossification (HO) is a known sequela in total ankle arthroplasty. The purpose of this study was to determine the radiographic incidence of HO in fourth-generation total ankle implants including the INFINITY, CADENCE, and VANTAGE. Radiographs were assessed for the incidence and location of HO in each implant using the modified Brooker classification. Seventy-one patients were included. There were 41 INFINITY, 16 CADENCE, and 14 VANTAGE implants. The average radiographic follow-up was 19.7 months. The incidence of HO was 69.0%. Overall, the HO was Class I in 31 cases (63.3%); Class II in 7 cases (14.3%); Class III in 10 cases (20.4%); and Class IV in 1 case (2.0%). For INFINITY; n = 33 patients (80.5%), CADENCE; n = 8 patients (50%); VANTAGE n = 8 patients (57.1%). When comparing INFINITY with CADENCE/VANTAGE, there was a statistically significant difference in presence of HO (P = 0.01). When comparing INFINITY with CADENCE, there was a statistically significant difference in presence of HO (P = 0.04). In the 33 cases of INFINITY with HO, 30 had neutral or posterior coverage, and in 4 cases, the prosthesis did not extend to the posterior tibial cortex (P = 0.005). This study demonstrates a continued high rate of HO with 3 fourth-generation ankle implants in the short term, although many were Class 1 and posterior. The INFINITY had a higher overall incidence of HO. Adequate posterior cortical coverage did not play a role in radiographic presence of HO. Further research is warranted with longer-term follow-up to determine the clinical and radiographic significance of HO. Level of Evidence: Level III: Retrospective comparative