[Single- and double-coated star total ankle replacements: a clinical and radiographic follow-up study of 109 cases].
An up to 12-year follow-up of 51 single-coated STAR revealed that 15 ankles had undergone fusion. The mean time from primary surgery to the first revision was median 51 months. In a series of 58 double-coated STAR ankles followed up to 5 years only one ankle had to be revised for component loosening. In this series the clinical survival rate was 98% and the radiographic survival rate 94% at 5 years. The radiographic survival rate, with component loosening as endpoint, was significantly better for the last 31 cases in the series of the single-coated prostheses. However, the loosening rate did not differ when these latter 31 cases were compared with the cases operated on with a double-coated prosthesis. One may conclude that improvement of the anchoring surfaces has had a limited influence on the radiographic survival of the STAR ankle. However, from the clinical survivorship figures it is obvious that the learning process continues as the difference in revision rate between the 31 last implanted single-coated and the later on implanted double-coated prostheses approached significance.