Implications of subtalar joint anatomic variation in calcaneal lengthening osteotomy

The purpose of this study was to identify the percentage of individuals with distinct anterior and middle calcaneal facets. Calcaneal lengthening osteotomy, as popularized by Mosca, is extra-articular, with its site being the interval between the anterior and middle calcaneal facets. For individuals without a distinct anterior and middle facet, the subtalar joint must be violated to perform this operation. The authors studied 1,056 calcanei in 528 human cadavers from the Hamann-Todd Osteology Collection at the Cleveland Museum of Natural History. Findings were categorized using the Bunning and Barnett classification of subtalar facet configuration. Type A was found in 389 calcanei (37%), type B in 480 calcanei (46%), and type C in only two calcanei. Transitional type was found in 122 calcanei (12%). There was no anterior facet in 61 calcanei (6%). Asymmetry was found in 51 cadavers (10%). Most calcaneal lengthening osteotomies will occur intra-articularly, which may affect clinical results.