Two and three-dimensional CT mapping of the sustentacular fragment in intra-articular calcaneal fractures.

The sustentaculum tali are tightly bound to the talus by the interosseous and deltoid ligament complex and have been considered a ''constant fragment". Yet there is a dearth of study on the anatomical patterns of the sustentacular segment. Consequently, this study is designated with the purpose of defining the prevalence and displacement of sustentacular fractures in intra-articular calcaneal fractures (ICFs) applying computed tomography (CT) mapping in both two-dimensional (2D) and three-dimensional (3D) conditions. From January 2019 to December 2020, the CT images of sixty-seven patients with eighty-one ICFs were retrospectively evaluated, besides, basic patient demographics and mechanisms of injury were documented. And the prevalence of sustentacular fractures was characterized in the sagittal or coronal CT planes. The subluxation, angulation, and translation of the portion of the sustentacular bone were noted. By decreasing rebuilt fracture fragments to suit a model of the sustentaculum tali, a 3D map was generated. Overall, the sustentacular fracture in 21 (25.9%) of the 81 ICFs, 15 (71.4%) were nondisplaced, 6 (28.6%) were displaced, and mean coronal angulation was 21.9°, and no comminuted. The relationship between sustentaculum tali and the talus was anatomically aligned in 71 (87.7%), and subluxation in 10 (12.3%). According to the research, 3D mapping demonstrated that most fracture lines start from the anterior of the sustentaculum tali, extending obliquely to the sulcus of the flexor halluces longus tendon. Moreover, this study provides a detailed description (displacement or articular dislocation) of the frequency of sustentacular fragments in ICFs. The finding disproves the ''constant'' theory of the sustentacular fragments, due to the fact that comminuted fracture of sustentaculum tali was rare. And the expertise of these fracture patterns may affect the progress of fixation concepts and surgical approaches. Moreover, we further speculated that the displacement of the sustentacular fragment was considerably more probable to emerge in the higher-order Sanders classification. Nevertheless, bigger sample size is required to further validate this position.