A REVIEW OF CLASSIFICATION METHODS FOR AVASCULAR NECROSIS (AVN) ALLOWS FOR CROSS STUDY OUTCOME EVALUATION
Gordon N, Rajadhyaksha A, Jones LC , Etienne G, Mont M

Multiple classification systems are utilized in studying osteonecrosis of the hip, making cross-publication evaluation of results difficult. This study reviewed all of the available literature concerning outcomes of surgical treatment of osteonecrosis of the hip since 1985 (post-MRI) to analyze the spectrum of classification systems used and whether comparisons can be made to allow interpretation of cross-publication data. A PubMed search revealed 109 published reports of outcome studies concerning treatment methods of hip osteonecrosis. Twelve major classification systems were identified of which 8 had between one and three modifications utilized in various reports. Modifications included regrouping patients by further radiographic and MRI data. Eleven systems analyzed single factors such as MRI location, vascular supply, etc. and should not be considered as a classification system but as an adjunct. Four major classification systems encompassed over 80% of the reported studies. Similarities were found across all systems. A cross system analysis can be made if data is collected according to patient symptoms, magnetic resonance imaging findings, and x-ray findings which would allow for the use of any staging system.