Interest in mobile-bearing total ankle arthroplasty has increased in recent years. Clinical studies show favorable but varying results, with survival rates between 70% and 90% at 10-year followup. Design-specific differences in early migration patterns might explain variations in the results and modes of failure. Using radiostereometric analysis (RSA) we prospectively followed 15 RA patients with a cementless mobile-bearing total ankle arthroplasty. The American Orthopaedic Foot and Ankle Society ankle score and radiostereometric radiographs were evaluated immediately postoperatively, 6 weeks postoperatively, 3 months, 6 months, and 12 months postoperatively and yearly thereafter. The postoperative clinical results improved. We observed increased migration of the tibial component during the first 3 months, but this stabilized by the 6 month followup. The mean lateral-medial migration was 0.8 mm, distal-proximal migration was 0.9 mm, and posteroanterior migration was -0.5 mm. The latter implies the total resultant migration was in anterior and valgus tilting of this tibial component. However, migration stabilized at 6 months postoperatively. We believe the surgical technique (anterior cortical window for placement) and the method of tibial fixation likely explain this migration.
Level of evidence: Therapeutic, Level IV. See Guidelines for Authors for a complete description of levels of evidence.