OUTCOME SCORES AFTER ARTHROSCOPIC ANKLE FUSION REACH A STEADY STATE AFTER ONE YEAR, BUT REVISIONS OCCUR LATER: PROSPECTIVE ANALYSIS

Introduction: Outcome studies need to follow patients until a point at which the outcome is stable in either retrospective or prospective studies. The longer the time period of follow up the more likely patients will be lost to follow up. Revisions of the primary procedure may take months to years to occur. The purpose of this paper is to determine when scores stabilize after arthroscopic ankle fusion, and the distribution of time to revision. Method: Patients undergoing arthroscopic ankle fusion at one institution performed by four fellowship trained Orthopaedic surgeons were recruited and prospectively followed. Annual outcome scores were obtained. This included AOS, expectation, satisfaction, and SF 36 scores. Statistical analysis was performed to determine when each outcome score achieved a steady state. Results: 190 Arthroscopic ankle fusions were followed annually for an average of 7.2 years (range 1 to 15 years). The age at surgery was 58 +/-12 years, BMI 28.9 +/- 5.5, 66% male, 11% diabetes, and 6% smokers. There were 103 COFAS type 1, 41 type 2, 15 type 3 and 31 type 4. 5 revision fusions were performed, and 29 reoperations performed (most for hardware removal). The AOS score improved after surgery at 6 months and 1 year and was stable thereafter. The SF 36 PCS score stabilized by 6 months. The expectation score stabilized at 6 months, The satisfaction score, stiffness score and swelling score all at 1 year. Revisions on the other hand occur at an average of 2.5 years +/- 2.8 years. Conclusion: Prospective or retrospective data for outcomes for arthroscopic ankle arthrodesis only needs to be followed until 1 year. A similar result has been obtained for ankle replacement. However, if revisions are to be followed then longer term follow up is required.