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

Abstract

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 <0.0001). A low-signal intensity line on T1 and T2 weighted MR images and linear lucency on CT were the most common patterns of subchondral fracture. Conclusion: Our study showed significant relationship between BME and subchondral fracture/ femoral head collapse and supported the results of previous studies in considering BME as a marker for potential progression of osteonecrosis. ACTA MEDICA NAGASAKIENSIA 58: 13－18, 2013