Berndt Harty - Osteochondral Lesions of Talar Dome

Mansoor Ahmed

1. Anatomy - Thinnest cartilage located along most medial and lateral rim, thickest cartilage located in the center of the dome. Note: cartilage along the medial rim is thicker than cartilage along lateral rim.

2. Etiology - Overall, trauma is main cause. 30-40 percent of medial lesions may be associated with chronic overuse stress or vascular insufficiency.

3. Biomechanics - Talar dome is wider anteriorly. During dorsiflexion, it sits tightly in the ankle mortise, during plantarflexion, it sits loosely in the mortise. Medial lesions associated with torsional force, lateral lesions associated with shearing force. Dorsiflexion/inversion produce anterolateral lesions. Plantarflexion/inversion produce posteromedial lesions.

4. Shape/Location - Medial lesions more common than lateral, rarely occur in the center of the dome. Medial lesions are larger, extend further, more stable, less tendency to displace, and are cup shaped.

5. Presentation - Symptoms fail to resolve after 6-8 weeks of treatment, no specific physical exam finding.

6. Imaging - Commonly missed on acute films, especially stage 1 and 2. MRI good for evaluating cartilage and marrow edema. CT good for surgical planning.

7. Classification - Radiographic classification
Stage 1 - Transchondral lesion
Stage 2 - Partially detached fragment
Stage 3 - Completely detached, non displaced
Stage 4 - Detached, displaced
Stage 5 - Subchondral cyst (added by Loomer)

8. Treatment - First line of surgical treatment consists of debridement and drilling. Can use internal fixation if fragment is a large, viable flap. May also use autologous chondrocyte implantation if first line of surgical treatment fails.