Inter- and Intraobserver Reliability of the COFAS End-Stage Ankle Arthritis Classification System

Background: End-stage ankle arthritis should have an appropriate classification to assist surgeons in the management of end-stage ankle arthritis. Outcomes research also requires a classification system to stratify patients appropriately. Materials and Methods: Six fellowship trained foot and ankle surgeons met on two occasions to derive a classification system for end-stage ankle arthritis. A four-part classification system was designed. Four surgeons reviewed blinded patient profiles and radiographs on two occasions to determine the inter- and intraobserver reliability. Results: Good interobserver reliability ( kappa = 0.62) and intraobserver reproducibility ( kappa = 0.72) was demonstrated for the classification system. Conclusion: The COFAS classification system appears to be a valid tool for the management and research of end-stage ankle arthritis.