Relationship of Alignment and Tibial Cortical Coverage to Hypertrophic Bone Formation in Salto Talaris® Total Ankle Arthroplasty

Abstract

A retrospective analysis of 107 Salto Talaris® total ankle replacements was performed to determine the effect of alignment and tibial cortical coverage on the formation of heterotopic bone. The radiographic parameters were studied for at least 18 months to detect any changes over time. The angle of insertion of the implant was most often in varus and with a positive anterior slope. A slight increase was seen in the slope over time (p < .0001) but was not clinically relevant. The mean percentage of cortical coverage of the tibial component was 89%, and only 7 patients had complete coverage of both the anterior and the posterior cortices. The percentage of patients who had hypertrophic bone growth increased over time (p < .0001). As the slope of the implant increased, there was a negative correlation with the degree of tibial coverage (p = .007). There was also an increase in the extent of hypertrophic bone as the tibial coverage decreased. None of the patients had symptoms that required an additional surgical procedure. The results of the present study indicate a high incidence of hypertrophic bone proliferation when the dimensions of the tibial component do not match the anteroposterior depth of the tibia at the plane of resection. Despite the high occurrence rate, the clinical relevance of hypertrophic bone is obscure.