Fig. 3.

(A–B) Section of T₁-weighted coronal MRI and plain radiograph of a 61-year-old patient presenting with Steinberg stage II osteonecrosis of the femoral head (ONFH) in the left hip and 90% femoral head involvement (circle in panel A). (C–D) Follow-up section of T₁-weighted coronal MRI and plain radiograph of the same patient after treatment with oral acetylsalicylic acid (ASA) for < 12 months. The ONFH involvement of the femoral head increased, with evidence of subchondral collapse (circle in panel C) and progression to Steinberg stage IV ONFH.