Pseudarthrosis of the cartilaginous part of the first rib is a common incidental finding on chest CT.

PURPOSE The cartilaginous parts of the first rib are usually articulating with sternal manubrium via a synchondrosis. With advancing age, there is progressive calcification of the rib cartilage. Pseudarthrosis of this calcified cartilage have been described in a study on anatomic specimen, but there are no systematically studies examining the anatomy of the cartilaginous parts of the first rib in vivo or using computed tomography (CT). MATERIAL AND METHODS A retrospective study of 60 chest CT scans of patients without history of trauma was performed and 120 first ribs were examined. In all patients, the grade of calcifications of the first rib was determined (no calcifications/some calcifications/severe and at least on one side contiguous calcification of the cartilage) and the presence of pseudarthrosis was noted. RESULTS Pseudarthrosis was found in 39/120 ribs (32.5%). The occurrence of pseudarthrosis was significantly more common in patients with severe calcifications (54%) in contrast to patients with no or minor calcifications (6.1%). CONCLUSIONS Pseudarthrosis of the first rib is a common finding in patients with severe calcifications. Radiologists should be aware of this frequent incidental finding, that should not be mistaken for pathology in CT imaging after trauma.