Costal cartilage injury

Costal cartilage injuries occur in the cartilage connecting the ribs anteriorly to the sternum. They most commonly manifest as edema and fractures with the latter being the focus of this article. 

Epidemiology

There is little published data (c. 2021) on costal cartilage fractures. Most reported cases are in males and result from blunt trauma, fall or motor vehicle collision ^1,2,11. They can be associated with some contact sports such as hockey, wrestling, and American football ¹⁰.

Clinical presentation

In young children, a costal cartilage fracture can present as a chest wall mass associated with pain (differentials include neoplasm and post-traumatic hematoma). In older patients, pain is the primary complaint ^1,2 which can present months after the trauma ¹¹.

Pathology

Costal cartilage can fracture due to blunt trauma sustained in high-energy trauma or a fall. While the more immobile first and second ribs seem to be more prone to costochondral separation from twisting injuries (e.g. wrestling ¹⁰), the lower ribs can suffer costal cartilage fracturing more easily ¹ and are more likely to fracture due to direct trauma ¹⁰. 

Disruptions or fractures of costal cartilage may result in an unstable rib cage potentially exposing thoracic contents, such as the heart, to injury ¹.

Radiographic features

Plain radiograph

Fractures of the costal cartilage are challenging to establish on physical examination and are not visible on plain radiographs unless there is severe calcification of the cartilage ^3,4. Due to their low incidence, they may also be easily overlooked on additional imaging.

Ultrasound

Ultrasound can be used reliably to diagnose costal cartilage fractures and can increase the sensitivity of their detection when used together with CT scanning ^5,6. Unlike CT it does not involve ionizing radiation and is, therefore, preferable in a pediatric population and for follow-up examinations ^1,7. Furthermore, it may be helpful to perform an ultrasound examination when there is a high clinical suspicion, with or without a mass, and other modalities have not demonstrated an injury ³.

Signs of a cartilage fracture include a fracture line, disruption of the anterior echogenic margin, a step-off deformity, or gas located at the costochondral junction ^2,3. Ultrasound also has the advantage of being a dynamic examination that can detect abnormal movement at the fracture site ¹¹.

Pitfalls include ⁶:

• confusion of the pleural surface with rib cortex

• misinterpretation as a fracture due to:

  • transducer overlying a rib and either an intercostal space or scapula

  • costal cartilage calcifications parallel to the rib surface (less likely in the pediatric population)

CT

CT is a reliable method of identifying costal cartilage fractures ¹. They tend to be mid-substance (i.e. in the center of the costal cartilage), and healing costal cartilage fractures display linear calcifications (vertical at the fracture, horizontal at the perichondrium ¹¹. CT offers the advantage of demonstrating other injuries, such as rib fractures and involvement of lung parenchyma.

MRI

MRI can demonstrate costal cartilage fractures best on T2 sequences with edema seen on T2 fat-saturated sequences ^10,11. Like ultrasound, MRI lacks exposure to ionizing radiation.

Treatment and prognosis

It is unclear if costal cartilage fractures completely heal ⁸, but reported cases state a return to normal sports activities when the pain goes away ^1,7,9. It is not known if the supposedly healed cartilage can sustain the same loads as the original cartilage. When returning to sports, especially contact sports at risk for direct trauma (e.g. hockey, rugby), protective padding may be used for an additional period as a precaution to allow for further healing while reducing the risk of any repeated injury.

Differential diagnosis

• costochondral separation injury