"The ARCO classification was created in 1994 and is periodically revised. The revision from 2019 is based on features of x-rays, CT and MRI 1,3, simplifying the system into four stages (I-IV) and no longer incorporating subclassifications of location and size 3. ARCO subsequently published a separate classification of lesion size and location for pre-collapse disease in 2021 (types 1-3, based on the lateral extent of the necrotic lesion on coronal CT) 4."
"This classification is in increasing use (c. 2026), as it can be applied across imaging modalities and discriminates between pre-collapse and post-collapse disease 2."
"This classification is in increasing use (c. 2026), as it can be applied across imaging modalities and discriminates between pre-collapse and post-collapse disease 2."
"stage II: abnormal on x-ray (osteosclerosis, focal osteoporosis or cystic change) without subchondral fracture, fracture of the necrotic portion or femoral head flattening"
"The ARCO classification was created in 1994 and is periodically revised. The revision from 2019 is based on features of x-rays, CT and MRI 1,3, simplifying the system into four stages (I-IV) and no longer incorporating subclassifications of location and size 3. ARCO subsequently published a separate classification of lesion size and location for pre-collapse disease in 2021 (types 1-3, based on the lateral extent of the necrotic lesion on coronal CT) 4."
"The 2019 revised system has four stages, defined on x-ray, CT and MRI 1,3:"