High-signal T2 changes of the bone marrow of the foot and ankle in children: Red marrow or traumatic changes?

Background: High-signal T2-weighted bone marrow changes can be found in both bone marrow edema and hematopoietic marrow and are often seen on pediatric MR images of the feet and ankle. Objective: To evaluate whether high-signal T2 changes of the bone marrow seen on pediatric MRI of feet and ankles represent residual hematopoietic marrow. Materials and methods: A total of 402 bones in 41 pediatric MRI studies of feet and ankles (34 children, 1-18 years) were reviewed by two observers who were blinded to the patients' ages. The studies were reviewed for the presence of high-signal changes of the bone marrow on sagittal fluid-sensitive images. The frequency and location of these foci were correlated with the patients' ages. Results: High-signal T2 changes of the bone marrow were seen in 45/402 bones (11%) and in 24/41 patients younger than 16 years (59%). The changes were most commonly located in the calcaneus (54%), followed by the talus (35%) and navicular bone (35%), invariably at the endosteal surface. In 16 ankles, such foci were seen in the feet but not in the distal tibia/fibula. Symmetric presence (two ankles) or absence (four ankles) of high-signal marrow were seen in six of seven patients with bilateral ankles. Conclusion: High-signal T2 changes of the bone marrow in pediatric feet and ankle MRIs have a symmetric, fairly consistent pattern and disappear after the age of 15 years. We believe that these high-signal areas are normal and represent residual hematopoietic marrow.