Bone marrow edema syndrome of the foot and ankle

Bone marrow edema syndrome of the foot and ankle, also known as transient bone marrow edema syndrome of the foot and ankle, refers to the presence of self-limited, patchy bone marrow T2 hyperintensities in the bones of the ankle and/or foot of unknown etiology. It is related to transient osteoporosis of the hip and regional migratory osteoporosis, which together are thought to form a single entity with different manifestations.

Epidemiology

Middle-age men are more commonly affected, with a male to female ratio of 3:1. However, young women, especially at the third trimester of pregnancy, can also be affected ¹. It is rare in children.

Clinical presentation

Patients have an inflammatory pattern of pain, with an acute or insidious onset that progressively worsens, reaches a plateau in 1-2 months, and then slowly regresses in the next 4-8 months.

Laboratory tests are normal, including acute phase reactants. 

Pathology

Vitamin D deficiency may appear in up to 61% of the patients ². The association between low vitamin D and the pathophysiology of bone marrow edema syndrome is still unclear.

Samples from patients suffering bone marrow edema syndrome of the hip demonstrate patchy areas of increased interstitial fluid, dilated medullary sinuses, adipocyte necrosis and/or fibrovascular regeneration. There is a normal or even elevated osteoid formation, which is under mineralized with a decreased hydroxyapatite content ^1,5.

Transient ischemia with posterior reactive vasodilatation and altered biomechanics have been proposed as causative factors ⁵.

Radiographic Features

The talus is the most frequently affected bone, followed by the navicular, cuneiform, and forefoot bones ^1,3. However, any bone of the ankle and foot, isolated or in combination, can be involved. Apart from the ankle and foot, other bones may be affected, such as the hips and knees. When the findings move from joint to joint, this entity has been termed regional migratory osteoporosis.

Plain radiograph

Initially, conventional radiographs are normal. Various degrees of radiolucency (regional osteopenia) can develop during the first months of the disease.

MRI

• T2 or STIR: diffuse or patchy bone marrow edema
• joint effusions and soft tissue edema may also appear

Nuclear medicine

Bone scintigraphy shows intense increased uptake.

Differential diagnosis

The diagnosis of bone marrow edema syndrome requires one to rule out causes of secondary bone marrow edema ^2,8, such as trauma, stress fractures, osteochondral lesions, infection, impingement syndromes, avascular necrosis, arthropathies, radiotherapy, and neoplasia, including bone metastases. In most cases, clinical data is of paramount importance to do so.

Differentiation from complex regional pain syndrome (Sudeck atrophy) may be difficult ³. Features that point to this condition are:

• history of prior trauma or immobilization
• skin changes on physical exam, with skin thickening and soft tissue edema on MRI
• muscle atrophy in chronic stages
• subcortical bone is predominantly affected