Prediction of the exposure range of the talar dome in open surgery for osteochondral lesions of the talus

OBJECTIVES: To assess the exposure range of the talar dome during open surgery for osteochondral lesions of the talus (OLT) by simulating the maximum flexion and extension of the ankle joint and anterior half medial malleolar osteotomy using digital methods and cadaver experiments. METHODS: Sixty sets of CT scan data from normal ankle joints of Chinese adults were randomly selected. Digital methods were used to simulate maximum dorsiflexion, maximum plantarflexion, and anterior half medial malleolar osteotomy. The exposure ratios for the talar dome at the 1/6, 1/4, 1/2, 3/4, and 5/6 longitudinal lines (A‒P line) were measured under direct visualization and verified through cadaveric experiments. RESULTS: A total of 58 ankle joint CT datasets and 8 cadaveric ankle joint specimens were included in the study. Under direct visualization, maximum plantarflexion exposed the anterior portion of the talar dome, with the following exposure ratios for the 1/6, 1/4, 1/2, 3/4, and 5/6 A‒P lines: 51.11%, 54.35%; 49.51%, 52.88%; 47.5%, 50.49%; 51.53%, 50.49%; and 52.68%, 51.26%, respectively. In maximum plantarflexion combined with an anterior half medial malleolar osteotomy, the exposure at the 1/6 A‒P line was 81.15% and 80.91%, respectively. During maximum dorsiflexion, the exposure ratios for the 1/6, 1/4, 1/2, 3/4, and 5/6 A‒P lines of the posterior talar dome were: 31.8%, 31.04%; 30.84%, 30.44%; 25.85%, 27.98%; 19.59%, 23.63%; and 17.96%, 20.17%, respectively. CONCLUSION: Digital simulation and cadaveric experiments provide useful references for selecting the surgical approach for open surgery for OLT. When the OLT lesion is located in the anterior half of the talar dome, exposure can be achieved without osteotomy in maximum plantarflexion. When the lesion is located in the posterior 30% of the medial region, maximum dorsiflexion can provide exposure. For lesions in the medial-mid to posterior region (50‒80%) of the talar dome, anterior half medial malleolar osteotomy can be applied to avoid a full medial malleolar osteotomy, but this approach is not suitable for posteromedial lesions located in the central-lateral region of the talar dome.