The Ribs: Anatomic and Radiologic Considerations

Abstract

The ribs are essential structures of the osseous thorax and provide information that aids in the interpretation of radiologic images. Techniques for making precise identification of the ribs are useful in detection of rib lesions and localization of lung lesions. The big rib sign and the vertical displacement sign can be used to differentiate the right and left ribs on lateral chest radiographs. The clavicle, the xiphoid process, and the sternal angle may be used as anatomic landmarks for rib counting on computed tomographic scans. For rib counting on lateral chest radiographs, the sternal angle or the 12th rib may be used. Anatomic rib variants include developmental deformities, cervical rib, and short rib and may mimic true rib diseases. Detection of thoracic deformities such as funnel chest (pectus excavatum) and barrel-shaped thorax requires an awareness of the strong correlation between the transverse appearance of the thorax and costal shape. Shadows around the rib cage (eg, rib companion shadows, sharp lines along the lower margin of the ribs, rib overlying shadows) may mimic pleural and extrapleural disease on frontal chest radiographs. It is imperative that the radiologist be familiar with normal rib anatomy, normal rib variants, and the radiologic appearance of the ribs to prevent misdiagnosis.

Costal Abnormalities

“…Kırk bin sağlıklı genç erkeğin akciğer grafilerinin değerlendirilmesinde konjenital kosta anomali sıklığı %1,4 bulunmuştur. 4,5,6 Servikal Kosta Servikal kosta 7. servikal vertebradan kaynaklanan aksesuar ya da fazladan kostadır. Bilateral ya da unilateral olarak ve değişen boyutlarda bulunabilmektedir.…”

“…İki kol arasında nabız yoğunluğunda farklılık oluşturur ve tanıda anjiyografi yardımcı olur. 6 Seçilmiş hastalarda servikal kostanın çıkarılması tedavi edici olmaktadır. 8 Çatal Kosta (Bifid Kosta) Erkek olgularda %0,6 oranında görüldüğü bildirilmiştir.…”

Methods of Counting Ribs on Chest CT: The Modified Sternomanubrial Approach

“…and counting the costal cartilages and ribs on the same axial images may be confusing due to reverse order, and, in rare cases, the eighth costal cartilage sticks to the xiphoid process and this may be confused with the seventh costal cartilage (5). However, in our study, this method was more accurate (95.6%) than the sternoclavicular approach.…”

Fusion of Ribs Mimicking Cavitary Lession

“…[1] In a study, 40.000 healthy subjects were screened and rib fusion was found to be the most frequent anomaly after bifid rib. [2] The incidence of bifid rib was reported as 0.6% while fusion of ribs as 0.3%.…”

“…Bifid rib, cervical rib, fusion of ribs are the most common costal anomalies. [1] Fusion of ribs may be segmental or it may affect the entire rib. Rib anomalies are often asymptomatic and they are incidentally determined on plain chest radiography performed for any indication.…”