Abstract
Category:
Ankle Arthritis
Introduction/Purpose:
Total ankle arthroplasty (TAA) remains a relatively uncommon procedure in New Zealand compared to total hip arthroplasty (THA) and total knee arthroplasty (TKA). Survivorship and clinical results of TAA have been mixed and inferior to both THA and TKA. There is a relative paucity of large series with long-term follow-up. The Salto mobile bearing prosthesis is now the most common prosthesis for TAA in New Zealand. We analysed a large series from a single surgeon with the purpose of reporting mid- to long-term survivorship, and performing radiographic analysis for radiolucencies and cytic changes.
Methods:
The New Zealand joint registry (NZJR) was used to obtain all Salto mobile bearing ankle replacements performed by the senior author between November 2005 and June 2012. The NZJR is a nationwide register of all joint arthroplasties performed in New Zealand and data on TAA has been collected since January 2000. Individual notes on each patient were reviewed to verify revision rate and reasons for revision. Post-op radiographs were analysed for alignment, radiolucencies, cystic changes and subsidence.
Results:
Of the 165 Salto mobile bearing ankle replacements in 150 patients, 62% were performed in males and 38% in females. Mean age at TAA was 65 years. Follow-up ranged from 5 to 121 months. Indications for primary included primary osteoarthritis (85%), inflammatory arthritis (9%), and post-traumatic arthritis (6%). 8% of patients (12 ankles) deceased during the follow-up although none had undergone revision. Over the course of the study, 8 ankles were revised giving a revision rate of 4.8% with mean time till revision of 69 months. Reasons for revision included aseptic loosening (3 ankles), talar collapse/avascular necrosis (2 ankles), broken polyethylene spacer without exchange of either component (2 ankles) and infection (1 ankle). At the time of study completion, 145 ankle replacements were still implanted in 130 patients which represents 94.7% survivorship in those patients still living. Post-operative radiographs demonstrated mean tibial alignment 90.7°, talar alignment 90.1°, tibial slope 82.6°, and talocalcaneal angle 11.2°. 49.1% demonstrated radiolucencies and 27.6% demonstrated cystic changes at long term. 7.2% showed subsidence over time.
Conclusion:
Our data represents one of the longest follow-up studies of the Salto mobile bearing TAA in the world. Our results show acceptable mid- to long-term survivorship. There is a notable percentage with radiolucencies and cystic changes but this does not seem to correlate with early failure. Component migration is uncommon. Further long-term follow-up of this cohort is necessary to determine the significance of the radiolucencies and cystic changes.