Heterotopic ossification following total ankle replacement: clinical significance and factors affecting its formation

Little is known about the clinical significance of heterotopic ossification after total ankle replacement and the factors contributing to its occurrence. This study documented the incidence of heterotopic ossification in a large ankle arthroplasty series; identified potentially related patient, implant, and operative factors; and determined the strength of association of those factors with the clinical outcome. Ninety ankles in 88 primary ankle arthroplasty patients were followed for an average of 32.4 months. Scandinavian Total Ankle Replacement, Salto-Talaris, and INBONE ankle implants were used at the surgeon's discretion. Heterotopic ossification was measured and classified using methods previously described for total hip arthroplasty. Incidence, location, severity, predisposing factors, and outcomes were documented, and correlation between ossification severity and each examined factor was determined. Eighty percent and 95.6% of ankles showed heterotopic ossification on anteroposterior and lateral views, respectively, and 97.8% showed evidence on either anteroposterior or lateral views. Ossification grades 4 and 3 were most common, predominantly located at the medial gutter and posterior to the tibial component. No preoperative variables were associated with heterotopic ossification, but its presence on lateral radiographs correlated with insufficient coverage of the tibial or talar component. Only three ankles required heterotopic ossification resection because of recalcitrant pain. The incidence of heterotopic ossification following primary total ankle arthroplasty was higher in this series than previously reported.