These lesions are segments of avascular bone that occur on the anterolateral and posteromedial aspects of the talar dome. The talus accounts for about 4% of all lesions. Lesions are thought to be of traumatic origin. Vascular variations and genetic factors may contribute. Often lesions occur with no trauma history. In children, the gender incidence is about equal. The onset may occur late in the first decade but is most common during the teen years.
Ankle pain, swelling, stiffness, and a trauma history suggest this diagnosis.
Imaging The mortis view may show the lesion best. CT and MRI may be helpful to assess the extent of the lesion and cartilage status if operative management is being considered. Most lesions are medial.
Classification Lesions are classifed into four categories.
- Stage 1 Subchondral osteonecrosis. Lesion is undisplaced and stable.
- Stage 2 The lesion is demarcated from the talus, but stabilized by the articular cartilage.
- Stage 3 The lesion is loose with disruption of the articular cartilage, but the lesion is not grossly displaced.
- Stage 4 The fragment becomes a loose body in the joint.
Management of Osteochondritis Dissecans
Manage most lesions in children with limitation of activity and immobilization. Lateral, sclerotic lesions that are separated are most likely to require surgery.
Stage 1 and 2 lesions Manage with activity modification, non-steroidal antiinflammatory drugs (NSAIDs), and time. Consider immobizing in a short-leg cast for 4 to 6 weeks. Manage persisting type 2 lesions with retrograde drilling.
Stage 3 lesions Manage by reduction and immobilization of the fragment. The options for stabilization include bioabsorbable implants, bone pegs, wires, or screws.
Stage 4 lesions Approach by arthroscopy or with the aid of a transmalleolar osteotomy. Excise small fragment. Treat larger lesions with excision, curettage, and cancellous grafting. For large lesions, consider mosaicplasty using autogenous osteocartilaginous grafts taken from the non-weight-bearing cartilage of the ipsilateral knee.
Good to excellent results are expected for type 1 and 2 lesions. Medial lesions do less well than lateral lesions. Lesions that result in loss of the articular cartilage often lead to osteoarthritis and the need for ankle fusion or replacement.