Review Question - QID 218713

The patient has an osteochondral lesion of the medial talus that is < 1cm in size with concomitant lateral ligamentous insufficiency (as evidenced by his talar tilt and anterior drawer testing), which has been associated with increased clinical failure rates when left unaddressed in the setting of osteochondral lesion repair.

Osteochondral lesions of the talus represent focal injuries to the talar dome with variable involvement of the subchondral bone and cartilage, most often due to repetitive microtrauma without a distinct history of ankle trauma when involving the medial talar dome. Diagnosis can be made with plain radiographs, but an MRI is obtained to determine the size of the lesion and the extent of associated bony edema, as well as to identify the presence of subchondral fluid indicative of instability of the lesion. Treatment is variable, but small (<1 cm), chronic lesions can typically be treated with arthroscopic debridement and marrow stimulation with the removal of any loose bodies that cannot be fixed. Larger (>1cm), displaced lesions often require more extensive procedures such as osteochondral allografting or autologous chondrocyte implantation (MACI) procedures. Regardless of the primary treatment for the osteochondral defect, it is essential to rule out any concomitant ankle ligamentous instability that would benefit from surgical attention, given that studies have shown progression to larger-sized lesions (> 1.5cm) and bipolar lesions (of the medial malleolus and tibial plafond) when concurrent ankle instability is left unaddressed at the time of OCD repair.

Hembree et al. reviewed the MRI features of osteochondral lesions of the talus. The authors note that the stability of such lesions can be assessed based on four MRI criteria: presence or absence of cartilage defects, edema-like signal abnormality, T2 bright rim, and/or the presence of subchondral cysts. They concluded that despite prior teachings that talar osteochondral defects occur either anterolaterally or posteromedially, most lesions are actually located medially and centrally on the talar dome, with the second highest frequency found laterally and centrally.

Lee et al. compared the outcomes of osteochondral lesions of the talus with and without chronic lateral ankle instability. The authors reviewed 420 patients with osteochondral lesions of the talus who underwent primary arthroscopic marrow stimulation, 74 of which had concomitant chronic lateral ankle instability (CLAI). They found that in those with CLAI, exhibited a significantly increased proportion of failure (AOFAS score less than 80) and inferior outcomes in the FAOS for the sport and recreation subscale at the latest followup. They concluded that compared with osteochondral lesions in ankles without CLAI, osteochondral lesions in an unstable ankle had an increased proportion of larger lesions (150 mm2 or larger) and additional chondral lesions at the tip of the medial malleolus and the tibia plafond, while also displaying increased clinical failure rates and inferior performance in sport and recreational activities post-operatively.

Figures A and B represent T1-weighted coronal and PD fat-saturated sagittal MRI sequences of an ankle with an osteochondral defect of the medial talar dome.

Incorrect Answers:
Answer 1: There is no imaging that shows the peroneal tendons to be torn, but the physical exam indicates chronically torn and unstable lateral ankle ligaments that should be addressed with a reconstruction.
Answer 2: There is no indication that the deltoid ligament is torn and does not need to be addressed surgically in this case.
Answers 4 and 5: OATS is unlikely to be performed for the ankle, and an OCA would not be necessary in this small, < 1 cm lesion of the medial talar dome. Furthermore, it would fail to address the patient's symptomatic lateral ankle instability which could lead to clinical failure should one of these grafting options be performed without lateral ankle ligamentous reconstruction.