|Classification and external resources
Bifid rib at the right side seen on chest radiograph. The fourth rib splits in two towards the sternal end.
A bifid rib (bifurcated rib or sternum bifidum) is a congenital abnormality of the rib cage and associated muscles and nerves which occurs in about 1.2% of humans. Bifid ribs occur in up to 8.4% of Samoans. The sternal end of the rib is cleaved into two. It is usually unilateral.
Bifid ribs are usually asymptomatic, and are often discovered incidentally by chest X-ray. Effects of this neuroskeletal anomaly can include respiratory difficulties, neurological difficulties, limitations, and limited energy from the stress of needing to compensate for the neurophysiological difficulties. Another association is with cyst of the jaw which may become malignant and may be a part of nevoid basal cell carcinoma syndrome.