The optimal procedure for lateral column lengthening calcaneal osteotomy according to anatomical patterns of the subtalar joint: an anatomical study in the Chinese population

BACKGROUND: Lateral column lengthening calcaneal osteotomy is a powerful procedure for correcting forefoot abduction in flatfoot deformity. However, it involves the risk of damaging articular facets of the subtalar joint. The optimal method to avoid violating the subtalar joint during lateral column lengthening remained controversial in published reports, implying that the subtalar joint might present anatomical variations among different nationalities. Therefore, the objective of this study was to perform an anatomical study by targeting the healthy Chinese population for the purpose of identifying the optimal procedure for lateral column lengthening calcaneal osteotomy according to anatomical patterns of the subtalar joint. METHODS: A total of 72 ft from 70 fresh frozen cadavers were obtained from the Department of Anatomy of Central South University. For each foot, soft tissues were surgically removed from the bones, and the calcaneus was completely separated from other bones to recognize the anatomical features of the calcaneus. The distance between the calcaneocuboid joint and the articular facet of the subtalar joint was measured by digital calipers for further analysis. RESULTS: Out of the 72 ft, 36.1% had separated anterior and middle facets in the calcaneus, and 63.8% had partly or completely fused anterior and middle facets. In the calcanei with discrete facets, the mean distance from the calcaneocuboid joint to the proximal margin of the anterior facet was 12.75 ± 2.10 mm, and the mean width of the separation between the anterior and middle facets was 2.43 ± 1.41 mm. In the calcanei with partly or completely fused anterior and middle facets, the mean width of the narrowest part of the tarsal sinus was 5.81 ± 0.62 mm and 6.25 ± 0.35 mm, respectively. CONCLUSIONS: The anatomy of the subtalar joint presents significant individual variations in the Chinese population. Calcanei with partly or completely fused anterior and middle facets were observed in nearly two thirds of individuals. Since the modified Evans procedure might potentially incur damage to the subtalar joint facets, the Hintermann procedure or other modified extra-articular lateral column lengthening procedures may be more applicable to the Chinese population.