Intermediate to Long-Term Outcomes of Total Ankle Replacement with the Scandinavian Total Ankle Replacement (STAR)

Abstract

Background: The Scandinavian Total Ankle Replacement (STAR) prosthesis has been in clinical use since 1981, with investigational use in the U.S. since 1998. Few studies of the North American version of the STAR are available. This prospective cohort study analyzed intermediate to long-term outcomes of total ankle arthroplasty with use of the STAR prosthesis at two Canadian centers.

Methods: Consecutive patients who received the STAR prosthesis between 2001 and 2005 were enrolled at two large, urban teaching hospitals. Patients were annually evaluated clinically, and the Ankle Osteoarthritis Scale (AOS) and the Short Form (SF)-36 were administered.

Results: One hundred and eleven ankles underwent arthroplasty with the STAR prosthesis. One-half of the patients were male; the mean age was 61.9 ± 11.7 years. Sixty-eight of the ankles underwent a total of 121 additional procedures during ankle arthroplasty, including gastrocnemius release, subtalar arthrodesis, triple arthrodesis, tendoachilles lengthening, and removal of hardware. The mean duration of follow-up for all living patients without revision (seventy-three ankles) was 9.0 ± 1.0 years. Thirteen (12%) of the ankles required metal component revision at a mean of 4.3 ± 3.0 years (range, 0.6 to 10.2 years). Twenty (18%) of the prostheses underwent polyethylene bearing exchange, mostly due to fracture, at a mean of 5.2 ± 2.1 years (range, 1.5 to 9.3 years). Most (97%) of the revisions and exchanges occurred in patients with a diagnosis of primary, secondary, or posttraumatic osteoarthritis (p = 0.0003). The mean change from baseline to final follow-up was -36.5 ± 23.3 points for AOS pain, -38.6 ± 26.8 points for AOS disability, and 9.6 ± 10.3 points for the SF-36 physical component summary score. The SF-36 mental component summary score was unchanged.

Conclusions: Intermediate patient-reported outcomes were good after ankle arthroplasty with the STAR prosthesis performed by experienced surgeons, and long-term outcomes demonstrated a 12% rate of metal component revision and 18% rate of polyethylene bearing failure. The revision rate was substantially higher among the first twenty ankles than among subsequent ankles, but the early ankles had nearly two years' longer follow-up than subsequent ankles. Additional study to elucidate possible reasons for polyethylene bearing failure is warranted.

Level of evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.