Accessory anterolateral facet of the pediatric talus. An anatomic study.

Background: The accessory anterolateral talar facet may be associated with talocalcaneal impingement in the painful flatfoot. We performed an anatomic study to identify this accessory facet and its associated osteologic features.
Methods: Within the Hamann-Todd Human Osteological Collection, seventy-nine paired tali and calcanei were identified among forty-three skeletons from individuals who had had an average age of 13.4 years at the time of death. Each specimen was surveyed for an accessory anterolateral talar facet, a calcaneal neck anterior extension facet, a dorsal talar beak, and the talocalcaneal facet pattern. Measurements included the angle of Gissane, posterior facet inclination, calcaneal neck length, posterior facet length, overall calcaneal and talar lengths, and accessory facet dimensions. Lateral radiographs of specimens with accessory facets were made in neutral and everted subtalar alignment.
Results: An accessory anterolateral talar facet was identified in twenty-seven (34%) of the seventy-nine specimens and was large in two (2.5%). Of the thirty-six skeletons with paired specimens, fifteen had an accessory facet and, of those, ten had the finding bilaterally. Degenerative changes or tarsal coalitions were not observed. Lateral radiographs demonstrated that subtalar eversion obscured observation of the facet. The accessory facet was associated with greater mean age (16.7 compared with 10.9 years; p < 0.0001), male sex (63% compared with 21%; p = 0.011), and a smaller mean angle of Gissane (116.2 degrees compared with 122.2 degrees; p = 0.018). Relative accessory facet volume was positively correlated with increased relative calcaneal posterior facet length (r = 0.53, p = 0.029). The accessory facet was significantly associated with dorsal talar beaking (29% compared with 4%; p = 0.028).
Conclusions: An accessory anterolateral talar facet was found in 34% of the specimens in a pediatric osteologic collection. The facet was associated with male sex, a smaller angle of Gissane, and dorsal talar beaking.