Bone marrow edema and subchondral fracture in osteonecrosis of the femoral head: analysis with MRI and CT

Purpose: To study the relationship between bone marrow edema (BME) and subchondral fracture in osteonecrosis of the femoral head (ONFH), and to analyze MRI findings of subchondral fracture and correlate them with those of CT.Materials and Methods: Fifty seven hips in 38 patients with ONFH were studied retrospectively. Images were obtained with 1.5-T MRI unit and multidetector helical CT. Selected hips were divided into edema positive and edema negative groups. In each group presence or absence of subchondral fracture and/or collapse of femoral head was assessed, and the MR findings were compared with those of CT.Results: Thirty (52.6%) of 57 hips showed BME during the course of ONFH. In these edema positive group, 29 (96.7%) of 30 hips showed subchondral fracture and/or femoral head collapse, whereas only 7 (25.9%) of 27 hips in edema negative group showed subchondral fracture and/or FH collapse (P