Does lateral column lengthening reach the ankle? Lateral calcaneal lengthening for flatfoot and medial talar dome osteochondral lesions: A weight-bearing CT 3D modelling analysis.

PURPOSE: Osteochondral lesions (OCL) of the medial talar dome are frequently observed in progressive collapsing foot deformity (PCFD), and hindfoot malalignment is believed to influence their natural history. It is not established whether, or to what extent, a realignment osteotomy modifies the articular relationship at the site of such a lesion, nor is there quantitative guidance on the size of opening wedge to be selected. METHODS: Starting from a severe PCFD case analysed via weight-bearing computed tomography, a 3D model was created using segmentation software. In the model, a lateral calcaneal lengthening osteotomy (LCLOT) was performed 15 mm proximally to the calcaneocuboid joint: Evans Technique. Three standard LCLOT-wedges (8-10-12 mm) were virtually applied at the osteotomy site. RESULTS: The 3D rotation of the anterior osteotomy stump with 8 mm wedge implied, with respect to the original talar position, 6.6° of dorsiflexion, 2.9° of inversion and 10.9° of external rotation; corresponding values for the ten and twelve mm wedges were 8.6°, 5.9° and 12.6°, and 14.2°, 10.2° and 22.2°. Further distance map analysis of the calcaneal posterior facet revealed a distancing effect on the posterolateral zone of the posterior subtalar joint with each wedge size. Additionally, the distance maps of the tibiotalar joint, where a concomitant medial osteochondral lesion of the talar dome was present, showed an increase in inter-surface distance between the medial talar zone and the mortise. This increase was progressively greater with the use of larger LCLOT wedges. CONCLUSIONS: The model confirms that Evans LCLOT produces a triplanar deformity correction, increasing the inter-surface distance at the anteromedial tibiotalar joint adjacent to the medial OCL. Patient-specific modelling may therefore inform preoperative planning when a talar dome OCL coexists with PCFD. LEVEL OF EVIDENCE: Level V, preclinical simulation study.