Heterotopic Ossification Following Total Ankle Arthroplasty With Fourth-Generation Prostheses.

Background: The purpose of the present study was to assess the radiographic incidence, location, and classification of heterotopic ossification (HO) in patients who underwent total ankle arthroplasty (TAA) with a 4th generation prostheses at a minimum of 1-year follow up. Baseline demographic, radiographic, and operative factors between patents with and without HO were compared.

Methods: Ninety ankles that underwent TAA with a 4th generation protheses, INFINITY (n = 62) or CADENCE (n = 28) were followed for an average of 23.7 (range, 12-49) months. Incidence and location of HO was assessed on weightbearing radiographs, and severity graded according to the modified Brooker classification. Data was compared between patents with and without HO to identity any predisposing factors.

Results: In 90 ankles that underwent 4th generation TAA, HO incidence was 55.6% (n = 50); 56.5% (n = 35) for INFINITY, and 53.6% (n = 15) for CADENCE. Twenty-five cases of HO were observed posteriorly, 16 anteriorly, and 9 combined. Severity was as follows; class I in 19 cases (38%), class II in 20 (40%), class III in 9 (18%) and class IV in 2 (4%). A single ankle required a non-revisional reoperation for HO debridement; reoperation rate of 2%.

Conclusion: The present study suggests a similarly high incidence of HO after TAA with two different 4th generation protheses (INFINITY 56.5%, CADENCE 53.6%). A trend for differences in location and severity between the protheses may also be present. Given the paucity of literature, additional studies with longer follow-up are warranted to discern the significance of HO following TAA with 4th generation protheses.

Level Of Evidence: Level III: Retrospective cohort study.