A randomised, controlled trial of two mobile-bearing total ankle replacements

Abstract

We describe the results of a randomised, prospective study of 200 ankle replacements carried out between March 2000 and July 2003 at a single centre to compare the Buechel-Pappas (BP) and the Scandinavian Total Ankle Replacement (STAR) implant with a minimum follow-up of 36 months. The two prostheses were similar in design consisting of three components with a meniscal polyethylene bearing which was highly congruent on its planar tibial surface and on its curved talar surface. However, the designs were markedly different with respect to the geometry of the articular surface of the talus and its overall shape. A total of 16 ankles (18%) was revised, of which 12 were from the BP group and four of the STAR group. The six-year survivorship of the BP design was 79% (95% confidence interval (CI) 63.4 to 88.5 and of the STAR 95% (95% CI 87.2 to 98.1). The difference did not reach statistical significance (p = 0.09). However, varus or valgus deformity before surgery did have a significant effect) (p = 0.02) on survivorship in both groups, with the likelihood of revision being directly proportional to the size of the angular deformity. Our findings support previous studies which suggested that total ankle replacement should be undertaken with extreme caution in the presence of marked varus or valgus deformity.

Total Ankle Replacement Compatible with Ligament Function Produces Mobility, Good Clinical Scores, and Low Complication Rates: An Early Clinical Assessment

“…Bearing movement on the tibia indicates that the rolling element of the natural movement of the talus on the tibia [11,33,34] is reproduced. We found no mention of bearing movement in any of the reports of the current three-component devices with anatomic talar and flat tibial components [3,6,7,25,30,31,[50][51][52][53][54]. The overall AOFAS score improved by a mean of 40.5 points (38.5 preoperatively to 79.0 at 48 months) and was similar to the 45-point increase of the meta-analysis [48].…”

“…Our data with 51 ankles at risk during the first year and a 4-year survival rate of 97.2% suggest few postoperative complications requiring component removal in contrast to reports from the registries [15,24,26] or from experienced surgeons [3,6,7,25,30,40,42,[51][52][53] (Fig. 7).…”

“…1) showed that to achieve ligament compatibility, either both fixed articular surfaces should have anatomic shapes or both should be nonanatomic [33,34]. Current three-part prostheses [3,6,7,25,30,31,[50][51][52][53][54] use a more or less natural-like convex surface for the talar component and a nonanatomic flat surface for the tibial component. We have shown this combination of anatomic and nonanatomic surfaces cannot reproduce isometricity of ligaments and therefore cannot be compatible with normal ligament function [33,34].…”

Rheumatoid Arthritis and Total Ankle Joint Replacement

“…Although studies have reported success rate of > 90% at 10 years using the STAR and Buechal Pappas (BP) implant [8], this data needs to be interpreted with caution as other studies using such implants are unable to reproduce similar success. Woods et al [9], an independent high volume unit, compared two different implants (STAR Vs BP) and reported only 79 % six year survivorship of the BP design as compared to 95% survivorship with the STAR design. This study had a relatively good sample of 200 patients, was a single centre study and was prospective in nature.…”

Total ankle replacement in moderate to severe varus deformity of the ankle

“…1,2 Relatively poor clinical results have been described in patients with severe pre-operative angular deformity, [1][2][3][4][5] and higher rates of complication occur in congruent varus ankles. 2 Some authors have suggested that the indication for operation should be narrowed to those with < 10° to 15° of varus or valgus [1][2][3][4][5] and good results have been reported following arthrodesis of the ankle in patients with severe varus or valgus deformities of the ankle. 6 Between 33% 3 and 44% 2 of patients with endstage osteoarthritis present with malalignment of > 10° in the coronal plane.…”