Pectus Carinatum (PC) is a structural deformity where the sternum and adjacent costal cartilages protrude outward, resembling the keel of a ship or the breast of a pigeon. It is the second most common chest wall deformity after Pectus Excavatum (sunken chest), typically affecting about one in 1,000 adolescents. Although often present from birth, PC usually becomes most noticeable and progresses rapidly during the growth spurts of puberty, affecting males more frequently than females.
Defining Pectus Carinatum and Its Variations
Pectus Carinatum is characterized by the excessive outward displacement of the sternum (breastbone) and the rib cartilage. This protrusion, resulting from an overgrowth of the costal cartilage, gives the condition its common names of “pigeon chest” or “keel chest.”
The condition is broadly categorized into two main morphological types based on the location of the greatest protrusion. The first and most common type is Chondrogladiolar prominence, where the middle and lower parts of the sternum jut forward. This type accounts for the vast majority of cases and is sometimes referred to as the central or lower type.
The second, less common type is Chondromanubrial prominence, also known as Pectus Arcuatum. In this variation, the upper part of the breastbone (manubrium) protrudes, sometimes accompanied by an indentation of the lower sternum. The protrusion can be symmetrical, involving both sides of the chest evenly, or asymmetrical, often with a slight tilt toward the right.
Etiology: Underlying Causes and Associated Syndromes
The precise cause of Pectus Carinatum remains unclear in most individuals, leading it to be classified as idiopathic. The leading hypothesis centers on a growth disturbance or overgrowth of the costal cartilage, which causes the cartilage to buckle and push the sternum outward.
Evidence suggests a significant genetic component, as up to a third of affected individuals have a family history of a chest wall abnormality. This familial tendency implies that inherited factors play a role in the development of the condition. The deformity is also frequently associated with various connective tissue disorders, which affect the body’s structural proteins.
Specific associated conditions include Marfan Syndrome, a disorder affecting connective tissue throughout the body, and Ehlers-Danlos Syndrome, which involves joint hypermobility and skin issues. Pectus Carinatum may also appear alongside other skeletal abnormalities like scoliosis, an abnormal curvature of the spine, and certain genetic syndromes such as Noonan Syndrome. The presence of these associations often prompts clinicians to screen for other underlying systemic conditions.
Functional and Psychological Impacts of the Condition
While Pectus Carinatum can be a prominent visual deformity, it typically causes fewer severe physiological issues than its counterpart, Pectus Excavatum. The outward rigidity of the chest wall can, in moderate to severe cases, prevent the chest from expanding fully during deep breaths. This reduced chest wall compliance can lead to less efficient respiration, causing some individuals to experience mild shortness of breath or decreased endurance during strenuous physical activity and exercise.
The most significant impact of Pectus Carinatum is often psychological and emotional, particularly for adolescents. The visible nature of the protrusion frequently leads to severe body image concerns and low self-esteem. Studies have shown that patients with PC may have a more significantly decreased mental quality of life compared to those with Pectus Excavatum.
Adolescents may actively avoid social situations or physical activities, such as swimming or gym class, where their chest might be exposed, due to embarrassment or fear of teasing. This self-consciousness can lead to social anxiety and withdrawal. Psychological distress can be a greater motivating factor for seeking treatment than any physical symptom, and counseling can be a beneficial component of care.
Clinical Pathway: Diagnosis and Management Strategies
The first step in the clinical pathway for Pectus Carinatum is a physical examination, as the diagnosis can often be made through visual inspection alone. The healthcare provider will assess the location and symmetry of the protrusion and may use specialized calipers to precisely measure the degree of the deformity. This initial assessment also includes a search for other features that might suggest an associated connective tissue disorder.
Imaging is often utilized to confirm the diagnosis, evaluate the severity, and rule out other underlying conditions. A chest X-ray provides a good initial view and can help detect conditions like scoliosis, which is sometimes seen with PC. Computed Tomography (CT) scans offer a detailed, three-dimensional view of the chest wall structure and are used to calculate severity indices, although their use is sometimes limited due to radiation exposure.
Management strategies are divided into non-surgical and surgical approaches. Non-surgical bracing is the preferred first-line treatment for most growing children and adolescents with flexible chest walls. An external brace applies continuous, focused pressure to the protruding area, gradually reshaping the cartilage over several months. This method is highly effective, with success rates often reaching 65 to 80% when patients are compliant and wear the brace for the prescribed hours each day.
Surgical correction is typically reserved for older patients with a rigid chest wall, severe deformities, or cases where bracing has failed. The most common surgical approach is a modified Ravitch procedure, which involves making an incision to remove the overgrown costal cartilage and reposition the sternum. A less invasive option, sometimes referred to as a Reverse Nuss procedure, involves placing a metal bar internally to push the sternum into a corrected position, which is then removed in a second surgery after a period of time.