Understanding Rib Anomalies

Introduction

Any anomalies in the ribs are by chance findings during imaging studies. As they are asymptomatic and nonspecific without causing any known harm to the individual, they are generally considered of less importance and are overlooked when they are not actively investigated. Many types of rib anomalies are present, which can be congenital (present during birth) or pathological (occurring due to pathologies/ diseases). Diagnosis of rib anomalies is done by multidetector computed tomography (MDCT).

What Is the Normal Anatomy of the Ribs?

There are twelve pairs of ribs in the thoracic cavity, including the sternum, the clavicles, and part of the spine. The ribs are elastic, flat bones attached to the sternum in the front and to the spinal bones in the back.

Based on their attachment to the sternum, ribs can be classified into the following types.

• True Ribs - The first seven ribs, which are directly attached to the sternum, are called true ribs.

• False Ribs - Ribs from eighth to tenth are false ribs that are attached indirectly via cartilage to the sternum.

• Floating Ribs —The last 11th and 12th ribs are floating ribs that are not attached to the sternum.

Based on their shape and size, they are divided into

• Typical Ribs - Ribs from third to tenth are called typical ribs as they have angular facets with long bodies.

• Atypical Ribs—The first two ribs and the last two ribs are considered atypical because they are different in morphology from other ribs.

What Are Rib Anomalies?

Any change from the normal anatomy or morphology of the ribs forming the ribcage is called a rib anomaly. Ribs are the main structures forming a bony cage around the most vital organs of the human body. Any changes in the presence of normal rib structures hampered the functions of the ribcage.

What Are the Causes of Rib Anomalies?

Rib anomalies usually occur at birth and are mostly due to disturbances in development, such as -

• Early fusion of the growth plate.

• Segmentation failure.

What Are the Various Types of Rib Anomalies?

Following are the types of rib anomalies:

• Calcifications of costochondral cartilages.

• Cervical rib.

• Short rib.

• Bifid rib.

• Intrathoracic rib.

• Rib fusion.

• Rib foramen.

• Rib notching.

• Calcifications of Costochondral Cartilages - These calcifications usually can occur at the second and third decades of life.

They can also be associated with conditions such as

• Renal failure.

• Thyroid diseases.

• Autoimmune diseases.

• Neoplasms.

• Cervical Rib—It is a supernumerary additional rib attached in the posterior region to the seventh spinal bone. Females tend to show a higher incidence of the cervical rib than males. It can be present either on one side, which is unilateral, or on both sides, which is bilateral. It does not show any symptoms but can be related to syndromes such as thoracic outlet syndrome.

• Short Rib—Also known as the hypoplastic rib, a short rib that cannot extend to the sternum is less common on the left side than on the right. In certain cases, it can also occur on both sides. It does not show any symptoms, and only one finding shows the presence of a short rib, but it is associated with syndromes such as Jeune syndrome and achondroplasia.

• Bifid Rib—This is also known as Luschka’s forked rib. It is a bone divided in the anterior region, usually affecting the fourth rib. It is usually asymptomatic but is associated with Gorlin syndrome.

• Intrathoracic Rib - It is a rare condition identified by a bony protuberance of the rib into the chest. It is commonly present on the right side of the chest and is a supernumerary rib.

It is further divided into subtypes, such as:

• Type Ia - Originating from the anterior and lateral portions of the vertebrae.

• Type Ib - Originating from the posterior region of the rib.

• Type II - It is a rare type that originates from another rib in the posterior region.

• Type III - Rib depression into the chest cavity comes under type III.

• Rib Fusion—The rib fusion can be partial or complete, affecting the anterior region of the rib.

• Rib Foramen—It is clinically not important as a defect but is used to diagnose bony lesions, cysts, and chondromas.

• Rib Notching—Rib notching anomalies are present on the surface of the ribs, causing increased pressure on the ribs.

What Are the Diagnostic Methods for Rib Anomalies?

• MDCT for Calcifications—Calcifications are seen as false joints and are visualized differently in males and females. Females have nodular central calcifications, while men show linear calcifications.

• MDCT for Cervical Rib: It shows the presence of an extra rib that is not attached to any bony structures anteriorly.

• MDCT of Short Rib- Shows the asymmetry between the short rib and the contralateral rib, along with regional changes in the ribcage.

• MDCT of Bifid Ribs - Visually, it is seen as a bifurcated rib attached to the sternum.

• MDCT of Rib Fusion - Fused ribs can be seen in the MDCT without causing much deformity in the ribcage.

What Are the Management Strategies for Rib Anomalies?

Most rib anomalies are asymptomatic and require little treatment, so they do not require specific treatments. Treatment begins only when the anomalies turn out to be infectious or cancerous lesions. Due to the changes in the morphology, discomfort can be managed by symptomatic treatment.

Conclusion

Rib anomalies rarely occur, and most of them occur congenitally. Due to a change in genetic behavior, such deformities occur. Most of them do not need treatment. However, it is necessary to be cautious about the syndromes associated with deformities, as they can pose more significant risks and require bigger treatments. It is never advised to delay treatment when any diagnosis is made that would require consulting a doctor.