A specific bone marrow edema around the foot and ankle following trauma and immobilization therapy: Pattern description and potential clinical relevance

Background: We describe a characteristic pattern of bone marrow edema about the foot and ankle seen by MRI in patients who have undergone recent immobilization therapy and investigate potential etiologies as well as possible clinical significance. Methods: Three reviewers retrospectively evaluated 52 ankle MRI examinations in 18 patients with abnormal signals compatible with bone marrow edema who had been treated with various types and durations of immobilization of the lower limb after traumatic injury. Bone marrow edema patterns were characterized by distribution, extent, location, and interval evolution or resolution on subsequent followup MRI examination. These MRI findings were then correlated with clinical history, symptomatology and treatment regimens. Results: All patients had a characteristic pattern of bone marrow edema about the foot and ankle predominating in subchondral, subcortical, and subenthesial locations. The occurrence of this edema pattern was most often noted on MRI within the first 12 weeks after completion of immobilization therapy or resumption of partial or full weight-bearing and did not correlate well with new symptomatology or pain. In patients with protracted imaging followup, the bone marrow edema ultimately resolved and was not associated with reported setbacks in recovery course or unexpected delays in restoration of function. All MRI examinations performed more than 18 weeks after the immobilization period showed resolution or stabilization of bone marrow signal, with no continued evolution. No patient had a clinical picture suspicious for reflex sympathetic dystrophy. Conclusions: A distinctive pattern of bone marrow edema on MRI of the foot and ankle can be seen on MRI after a variety of weightbearing and nonweightbearing immobilization therapies. This pattern has a consistent appearance on MRI and does not seem to be related to clinical symptomatology. At present, no substantial conclusions can be made regarding the etiology of this phenomenon. However, these bone marrow signal alterations should not mandate further imaging or a change in therapy on the basis of MRI findings alone.