Bifid rib

Clinical History

A 10-year-old male presented, who referred to the orthopaedic clinic, with a symptomatic chest wall lesion.

Imaging Findings

A 10-year-old boy presented with a lump on the right chest wall. This had been noticeable for over three years and had been slowly enlarging. It was tender when felt. An examination when done revealed the presence of a 6 x 4 x 3 cm swelling over the right anterior chest wall. An AP chest radiograph investigation showed that he had a bifid right third rib (Fig. 1).

Discussion

Bifid or forked ribs are known to occur in 3 to 6 per 1000 live births. In three cases of bifid ribs found at routine dissection, the third and fourth ribs were found to be involved. The distal parts of the osseous rib bifurcated at an angle of 60 degrees, and both of the branches had their own costal cartilages, and the arterial supply was from a small branch of the intercostal artery. The intercostal nerves did not bifurcate and continued along the lower margins of the lower branches of the bifid ribs. Bifid ribs may produce a noticeable chest wall swelling. If the patients are symptomatic, they are often referred for a specialist's opinion. Symptomatic chest wall swellings should be investigated further as in a histopathologcal study of samples aspirated from 227 chest wall lesions; 36% are malignant and 56% are benign lesions. Inflammatory lesions (54%) or lipomas (30%) are the commonest amongst benign lesions. Rare cases of tuberculosis involving the sternum, epithelioid leiomyosarcomas, and neuroendocrine tumors involving ribs, malignant nerve sheath tumors involving the chest wall, metastatic carcinomas of the stomach and the prostate, and papillary carcinoma thyroid have been reported in this series. Bifid ribs can be readily diagnosed on a plain chest radiograph (Fig.1) and this variant of the normal requires no intervention. Other normal rib variants include a discontinuity of the first rib, bridge formation anteriorly and forked rib anteriorly, small costal bridge, ridge shaped fusion anteriorly, fusion posteriorly, costal cartilage bridging or bifurcation and birurcated rib of Luschka. Asymptomatic chest wall swellings in children are usually related to normal variations in the bone or the cartilage of the chest wall. Bifid ribs are one of the skeletal abnormalities associated with the Gorlin–Goltz syndrome or the basal cell nevus syndrome. This condition, which has a prevalence of 1 in 60,000, is an autosomal dominant condition with incomplete penetrance. It comprises multiple nevoid basal cell carcinomatas, odontogenic keratocysts, palmar pits and ectopic calcification of the falx cerebri. Other skeletal abnormalities described are frontal and parietal bossing, hypertelorism and Sprengal’s deformity. The authors suggest that patients with a symptomatic chest wall swelling should be investigated initially with a plain chest radiography and if bifid ribs are noted, then the Gorlin–Goltz syndrome should be suspected and the condition be excluded by a further examination.

Differential Diagnosis List

Final Diagnosis

Bifid third rib.

URL:	https://www.eurorad.org/case/3020
DOI:	10.1594/EURORAD/CASE.3020
ISSN:	1563-4086