In brief: Ficat classification: avascular necrosis of the femoral head.

The earliest attempt at classifying avascular necrosis of the femoral head was proposed by Ficat and Arlet in 1964 [2], before the advent of MRI. The purpose of the classification was to provide prognostic insight and compare treatment options. Ficat modified the classification to include invasive testing procedures and a preclinical, preradiographic stage in 1985 [1]. Since then the system has been modified a few times to include MRI findings, patient symptoms, modify the description of radiographic findings, and exclude the invasive testing procedures originally described [13, 17]. In a systematic review of the literature, Mont et al. [13] identified 16 different classification systems used to classify and describe avascular necrosis. Of these, the Ficat classification [1, 2] was the most frequently used system (63%), followed by the University of Pennsylvania system [18] (20%), the Association Research Circulation Osseous (ARCO) system [4, 15] (12%), and the Japanese Orthopaedic Association system [7] (5%).