Rare case of rib-like ossification arising from a Y-shaped fourth costal cartilage

Abstract

I report a rare anatomical variant observed in a male cadaver in his 70s on postmortem computed tomography. The left fourth costal cartilage showed Y-shaped branching, with one branch exhibiting ossification that formed a rib-like structure extending laterally and terminating anteriorly in the third intercostal space. This ossified structure was continuous with the costal cartilage anteriorly but notably lacked continuity with the vertebral end of the rib or other posterior skeletal elements. Additionally, a costal cartilage foramen was incidentally observed in the right third rib, representing a potentially underrecognized anatomical variant. To the best of my knowledge, this specific configuration of Y-shaped cartilage branching with partial ossification and anterior truncation has not been previously described. Despite its uncertain clinical significance, the distinctive morphology may be valuable for personal identification using forensic imaging.