Anatomical characterization of the too-long anterior process of the calcaneum: a computed tomography scan analysis of 69 feet.

Our work aims to identify and measure the morpho-anatomical characteristics of too-long anterior calcaneal process based on computed tomography scans done in patients with a history of pain and who have experienced repeated ankle sprains. The computed tomography scans of 69 feet were reviewed. These scans were used to calculate (1) the calcaneo-navicular distance; (2) the height, length, and width of the too-long anterior calcaneal process; (3) the length of the calcaneum; (4) the angle of the too-long anterior calcaneal process in the sagittal (anterior-superior angle), axial (anterior-medial angle), and frontal plane. Out of 69 feet, forty-nine were pathological (71%) with abnormalities of the too-long anterior calcaneal process, while the rest (29%) had no morphological abnormalities. The calcaneo-navicular distance was found to be <5 mm (mean: 2.8 ± 1.2 mm) in all pathological feet, which also had significantly reduced calcaneo-navicular distance ( P < 0.001) and longer bone portion distal to the calcaneocuboid tangent ( P < 0.001) in comparison to normal feet. In pathological feet, the mean too-long anterior calcaneal process length was 10.7 ± 1.9 mm; the mean anterior-superior angle was 29.6 ° ± 11.6, the mean angle anterior-medial angle was 40.7 ° ± 8.3, the mean angle frontal plane was 74.2 ° ± 14.1. Similar to a cone or a parallelepiped, the too-long anterior calcaneal process has a complex three-dimensional anatomy, with a superior, medial, and anterior direction. Using the measurements obtained, four different too-long anterior calcaneal process morphotypes could be identified: absence of TLACP, triangular shape, rectangular shape, and coalition (level of evidence III).