Bone marrow lesions related to bone marrow edema syndromes and osteonecrosis

Abstract

Bone marrow lesions (BML) are abnormalities in the bone marrow identified on magnetic resonance imaging (MRI) and can generally be classified as traumatic or atraumatic. This review focuses on atraumatic bone marrow edema syndromes (BMES) and their imaging evaluation. The MRI remains the modality of choice for assessing BMES, particularly using fluid-sensitive sequences although other sequences such as Dixon and T1-weighted imaging can be of further assistance. Emerging evidence supports dual-energy CT (DECT) as a reliable alternative, with high sensitivity and specificity for detecting bone marrow edema. The term BMES is a collective term for conditions, such as transient osteoporosis (TO) and regional migratory osteoporosis (RMO), predominantly affect weight-bearing bones in middle-aged individuals and pregnant or postpartum females. Subchondral insufficiency fractures of the knee (SIFK) are a key subset of BMES. These fractures most commonly involve the medial femoral condyle (MFC) and are associated with risk factors, such as meniscal root tears and extrusion of the meniscal body. The MRI findings typically include bone marrow edema-like signals and subchondral fracture lines, with additional features, such as secondary osteonecrosis in advanced cases. Prognostic indicators are crucial for stratifying patients and guiding management. Low-grade or reversible lesions often resolve with conservative treatment, whereas high-grade or irreversible lesions may require surgical intervention.Avascular necrosis, another atraumatic BML entity, differs from BMES by its association with systemic factors, such as steroid use or alcohol abuse. Accurate imaging, particularly in the early stages, is vital to distinguish between reversible and irreversible lesions, facilitating timely and appropriate management.

Keywords: Avascular necrosis; Dual-energy computed tomography; Magnetic resonance imaging; Sensitivity and specificity; Subchondral insufficiency fracture of the knee.

Fig. 1

A 55-year-old patient with left hip pain related to reversible left hip bone marrow edema (BME) syndrome. a Frontal view dual-energy computed tomography with bone marrow algorithm shows bone marrow edema of the left femoral head (colored green, white arrow). b Fluid-sensitive magnetic resonance sequence performed 2 weeks later confirmed the bone marrow edema (white arrow). c T1-weighted Dixon in-phase image shows low signal, isointense to the adjacent muscles (white arrow). d The out of phase image shows a drop of signal of > 20%, indicating that there is no marrow replacement and that this is a benign lesion (white arrow). e Coronal fluid sensitive magnetic resonance image performed after 5 weeks demonstrates near complete resolution of the BME (white arrow). f Coronal T1WI after 5 weeks: the shape of the articular surface is maintained (white arrow)

Fig. 2

A reversible, low grade subchondral insufficiency fracture of the knee in the medial tibial plateau. a A coronal fluid sensitive magnetic resonance image. b A coronal T1WI. c A sagittal Proton Density weighted imaging. The classical triad of diffuse bone marrow edema, a subchondral fracture line (arrow) and medial meniscus body extrusion (arrowhead) is noted

Fig. 3

Irreversible, high grade subchondral insufficiency fracture of the knee of the medial femoral condyle (MFC). Coronal Proton Density with fat suppression (a) and T1-weighted imaging (b): there is diffuse bone marrow edema in the MFC (arrow). In addition, there is a band of low signal intensity compatible with osteonecrosis of the subchondral fragment (dotted arrow in a). Note the severe medial meniscal body extrusion (arrowhead). The contour of the articular surface is maintained. There is diffuse cartilage loss. Coronal proton density with fat suppression (c) and T1-weighted imaging (d) after 1 year. There is advanced osteoarthritis with complete cartilage loss, joint space narrowing and osteophytes

Fig. 4

Soft tissue findings associated with subchondral insufficiency fracture of the knee. a The metaphyseal burst sign. A coronal fluid sensitive image demonstrates soft tissue edema along the distal femoral metaphysis (arrows). b Edema is noted along the vastus medialis muscle on an axial fluid sensitive image (arrows). c A different patient. Characteristic soft tissue edema pattern with extensive edema abutting the posterior femoral cortex, extending along the vastus lateralis fascia is noted on an axial fluid sensitive image (arrowhead)

Fig. 5

Chronic avascular necrosis (AVN) of the left femoral head. Coronal T1-weighted (a) and fluid-sensitive sequence (b) frontal views. There is a serpentine line representing the border of the AVN (arrows). There is fatty replacement of the necrotized part. The articular surface has collapsed. Osteoarthritis with cartilage loss and joint synovitis are also seen