Osteochondral lesions of the talus: change in MRI findings over time in talar lesions without operative intervention and implications for staging systems.

BACKGROUND: MRI findings are used in several staging systems to help determine appropriate treatment. The purposes of this study were to evaluate longitudinal changes in MRI characteristics of osteochondral lesions of the talus (OLT) and to evaluate published staging systems in a cohort of nonoperatively treated patients.
METHODS: Twenty-nine patients were identified; MR images were reviewed for location, size, and interface signal of OLT as well as cysts, marrow edema and osteoarthritis. Lesions were classified as unchanged, progressed, or improved based on changes in size or interface signal. Each lesion was assigned a stage based on four different staging systems.
RESULTS: Of the 29 lesions, 13 progressed, seven improved, and nine were unchanged over an average followup of 13.7 months. In the 13 that progressed, marrow edema remained present in ten and developed in two. Four had persistent cysts and four developed new cysts. Two had progression of osteoarthritis and two developed it anew. In the seven that improved, six had some degree of marrow edema that persisted and one had a persistent cyst. Initial staging changed for at least one classification system in 16 (55%) of the 29 lesions at followup. Change in stage was primarily due to development (four of 16) or disappearance of cysts or progression of the lesion in the extent of bone marrow edema (five of 16).
CONCLUSIONS: OLT did not invariably progress over the short-term without operative intervention. Because some cysts and bone marrow edema resolved on MRI, they may not be reliable signs of lesion severity nor show progression of degenerative changes. Since these findings determine the stage and severity of OLT in some staging systems, they may require reconsideration and adjustment of the current staging systems.