Anatomical Variation in a Case of Bifid Rib

Background: This study involved a detailed dissection of a case of bifid rib with a focus on the structural aspects of the neurovasculature and musculoskeletal features. This study serves to add to the knowledge of the anatomical aspects of a rare rib dysfunction. This case is especially rare due to the Caucasian race of the cadaver. In this case the bifurcation was located on the right fourth rib at the costochondral junction. As with all other reported cases of bifid rib both internal and external intercostal muscles were present in the bifid space and the intercostal space above the bifurcation was reduced. Arterial supply was from an anastomosis of a branch off the third right anterior intercostal artery and a branch directly from the right internal thoracic artery. Innervation to the muscle of the bifid space was from a branch of the third intercostal nerve that branched in the lateral thorax and proceeded to run anteriorly along the superior aspect of the fourth rib. Conclusions: Bifid rib, along with other rib abnormalities are often asymptomatic but have shown an association with malignancy in childhood and other mesodermal developmental abnormalities. Knowledge of bifid rib is necessary when diagnosing chest wall and lung tumors as well as rib fractures due to the variability of the bifurcation.