The actual cause of pectus deformities is unknown. The usual explanation, for which there is some experimental evidence, is that there is overgrowth of the costal cartilages resulting in either protrusion or intrusion of the sternal elements.
Pectus excavatum (funnel chest)
|Pectus excavatum occurs when the cartilage overgrowth results in the sternal manubrium being forced back towards the vertebrae.
It is more common in males and frequently runs in families.
In severe cases the xiphisternum virtually touches the vertebrae, displacing the heart laterally, usually to the left. The excavatum deformity behaves as though there are attachments to the tendinous diaphragm and even the vertebrae. As the child grows around this attachment, the sternum and cartilages are drawn in. Eventually the ends of the ribs are drawn in and the chest cavity becomes elongated and flattened. The clavicular heads are drawn in when the deformity is severe. The appearance is of a tall thin male with a flattened elongated chest and a concavity at the lower end of the manubrium.
Patients are often referred because of their associated asthma, the deformity being blamed for the respiratory effects.
There is no evidence that it does. Others fear pressure on the heart.
Again the evidence is rather poor for any cardiac compromise, many a pectus patient being well able to run a marathon.
There is some evidence that severe deformities may impede right atrial filling at maximal exertion.
As the heart is rotated to the left in severe deformities, right axis deviation and tall P waves can be seen in lead II.
Pectus carinatum (pigeon chest)
Pectus carinatum is thought to have a similar aetiology to excavatum. However, there is no similarity to the diaphragmatic adhesion. As parents do not fear cardiac compression minor deformities are often well tolerated. As breast development progresses normally girls often do not mind a mild carinatum deformity.
To be truthful virtually all deformities are mixed to a degree with some rotation of the sternum. It should be expected and not regarded as a difficulty. Frequently the rotation is so slight it is best left alone. More extensive rotation will need to be corrected with imaginative osteotomies and wedges.
Pectus-like chest wall deformities often accompany Kypho-scoliosis. The deformity is usually unilateral and carinatum in nature. It is usually secondary to the vertebral rotation and is a rib deformity rather than a cartilage deformity. The deformity is exacerbated by the need for the lung to find some volume in which to operate. Therefore, any attempt to correct the deformity tends to fail as the lung re-expands and pushes the chest wall back out. To correct the deformity, rib osteotomies would need to be performed. This is virtually impossible to perform in flat bones.
Polands syndrome is a more extensive syndrome of defects of the chest wall. It includes loss of pectoralis major or minor muscles, hypogenesis or absence of the breast, absence of mammary and axilary hair, absence of costal cartilages and failure of the ribs to grow. Correction involves a combined procedure with the thoracic surgeon re-construcing the chest wall while the plastic surgeon performs an augmentation mammoplasty with latissimus muscle myocutaneous flap. The procedure must therefore be performed when growth is complete.
Agenesis of the sternum
Various degrees of sternal agenesis can occur with varying degrees of cardiac herniation. It is a rare congenital condition associated with craniofacial haemangiomata and omphalocele. It should be corrected in the neonatal period when the two halves of the sternum can usually be sutured together. Usually there are residual cartilaginous sternal bars connecting the rib ends.
In older children it may be necessary to perform slide chondroplasty accompanied by longitudinal osteotomies of the sternal bars to bring the two halves together. Skin cover may require omental or pectoral flaps. (See Cleft sternum and Sternal Foramen. Alexander A Forkin. In Surgical Treatment of Anterior Chest Wall deformities, Chest Surgery Clinics of North America, May 2000, 261 - 276)
Back to pectus index