Purpose: The global utilization of total ankle arthroplasty (TAR) has been increasing over the past decade; however there are a limited number of published prospective studies assessing intermediate and long term outcomes. The purpose of this clinical series is to prospectively review the mid-term clinical and radiographic outcomes of the Scandinavian Total Ankle Replacement (STAR) performed at two Academic Canadian University Centres.
Method: Between 1998 and 2005, 113 STARs were implanted into 99 patients at two Canadian centres. Prospective clinical and radiographic follow-up was performed. Validated and non-validated outcome questionnaires consisting of the AAOS foot and ankle questionnaire (a composite questionnaire made up of unaltered versions of the SF-36), AOFAS Hindfoot score, Foot Function Index (FFI), Ankle Osteoarthritis Scale (AOS) were completed in one arm (63/113 implanted TARs). In the other arm, (50/114) the patients were followed retrospectively with the same measures. Both groups had prospective radiographic follow-up using measures described by Wood et al.
Results: The average follow-up for both groups was 46.3 ± 17.6 months (or 3.8 years). Of the 113 implanted STARs, 33 (29.2%) required a re-operation. Of those, 20 (17.7%) went on to be revised. Six patients had repeat revision operations for a total of 26 revision operations. Of the 26 revision operations 14 (54%) were polyethylene liner exchanges, and 12 (46%) were revision of the metallic components. The median time to revision was 39.5 months. Three prosthesis (2.6%) went on to have a deep infection of their STAR. All three were effectively managed without requiring explantation of the STAR. One patient had infection in their revision IM Nail. Of the 113 initially implanted prostheses, 101 (89.3%) of the original TARs remained implanted at the conclusion of the study. Sustained benefit, across questionnaires, from the STAR was observed to persist to final follow up. 115/116 (99%) ankles followed showed evidence of osteolysis at the last STAR follow-up. The osteolysis was found to occur more commonly around the talar component, but occurred, for the most part, in a recognizable pattern around both the talus and the tibia. No significant differences between the two centers in pre-operative or intra-operative data were identified.
Conclusion: The STAR, in the mid-term, shows acceptable survival and revision rates. There are, however, some concerning findings on radiographic follow-up. It appears, upon initial investigation, that initial component position may be a factor that predicts concerning radiographic changes. Further investigation is required to substantiate this.
