Comparison of the short-term results of the first and last 50 Scandinavian total ankle replacements: assessment of the learning curve in a consecutive series.

Background: Total ankle replacement (TAR) is presently considered to be an acceptable alternative to ankle fusion for patients with debilitating conditions of the ankle. The placing of a total ankle prosthesis is a technically demanding procedure. We hypothesized that the challenging conditions could cause a longer learning curve (>30 cases), and therefore the short-term results of the first and the last 50 cases in a consecutive series of 134 cases were compared. Methods: The first and last consecutive 50 cases by a single surgeon in a series of 134 Scandinavian Total Ankle Replacements (STAR; Waldemar Link, Hamburg, Germany), inserted between May 1999 and May 2008, were evaluated. Operation characteristics, clinical outcome (Foot Function Index [FFI], Kofoed score), complications, and the component alignment on X-rays were assessed. The outcome measures for both groups were compared using independent Student t tests, chi-square tests, and nonparametric alternatives (P < .05). Results: Surgery time decreased from a median of 125 (83-160) to 100 (65-170) minutes (P < .001), and fewer perioperative complications were observed (12 vs 4, P = .04). The sagittal alignment of the tibial component was closer to normal in the last series (P < .001). The clinical outcome did not differ between the 2 series (median FFI: 32 [0-74] vs 25 [0-75], Kofoed score: median 71 [21-96] vs 80.5 [23-100]). The major underlying pathology did change from rheumatoid arthritis (60%) to osteoarthritis (44%; P = .002). No differences in type and number of complications were reported. Conclusion: The surgery time did decrease, there were fewer perioperative fractures, and the tibial component orientation improved, suggesting the presence of a learning curve. Operative experience and a shift in major underlying pathology did not influence clinical outcome. In view of this learning curve we suggest more restrictive patient selection for at least the first 50 TARs.