Congenital
Deformities of The Thoracic Cage
Pectus excavatum is also called
funnel chest, chonechondrosternon, or trichterbrust. It is a deformity of the
anterior chest wall characterized by depression of the lower sternum and
adjacent cartilages. The lowest point of the depression is at the junction of
the xiphoid process and the body of the sternum. The trait is inherited and may
coexist with other musculoskeletal malformations such as clubfoot, syndactyly,
and Klippel-Feil syndrome. The cause of funnel chest remains obscure. A short
central tendon and muscular imbalance of the diaphragm have been blamed. Most
current writers attribute the deformity to unbalanced growth in the
costochondral regions.
Symptoms are very uncommon.
However, a child with an obvious deformity may experience unfortunate
psychological effects. Funnel chest is usually associated with postural
disorders such as forward displacement of the neck and shoulders, upper
thoracic kyphosis, and a protuberant abdomen. Functional heart murmurs and
benign cardiac arrhythmias are frequently seen in these individuals, and the
electrocardiogram may show rightaxis deviation because of the displacement of
the heart. In older patients, there may be an appreciable incidence of chronic
bronchitis and bronchiectasis.
Depression of the sternum begins
typically at the junction of the manubrium and the gladiolus. The xiphoid
process may be bifid, twisted, or displaced to one side. Costal cartilages are
angulated internally, beginning with the second or third and extending caudally
to involve the remainder. In general, the defect tends to be symmetric, but one
side may be more depressed than the other so that the sternum deviates from the
middle line. An estimate of the cavitary volume may be obtained by filling the
depression with water while the patient lies supine. Standard radiographic films
reveal that the heart is displaced toward the left side, and lateral films show
the displacement of the body of the sternum posteriorly.
In patients who are symptomatic or
who show a significant progression of pectus excavatum, the deformity should be
corrected surgically. Because most of the operations are carried out with a
cosmetic end in mind, the results are best when surgery is performed between 3
and 7 years of age. Surgical correction consists of excision of the
hypertrophied costal cartilages on both sides; osteotomy of the sternum at the
junction of the manubrium and body; and then internal fixation by pins or rods,
which are removed later. Fixation by a metal strut or wire is required in older
patients to prevent recurrence of the deformity, which, in some degree, may
occur despite initial overcorrection.
Pectus Carinatum
Also known as pigeon breast,
chicken breast, or keel breast, this is a protrusion deformity of the anterior
chest wall that is unrelated to pectus excavatum and occurs about one-tenth as
often. Two principal types are recognized: (1) chondromanubrial, in which the
protuberance is maximal at the xiphoid and the gladiolus is directed
posteriorly so that a secondary saucerization is evident, and (2)
chondrogladiolar, in which the greatest prominence is at or near the gladiolus.
The pathogenesis is no better understood than that of pectus excavatum, but the
theory of unbalanced or excessive growth of the cartilages makes sense. Although
functional cardiac and respiratory difficulties have been observed, the chief
reason for surgical correction is cosmetic. If the deformity is minor, no
treatment is required. When operation is necessary, the procedure should be
tailored to the particular deformity, taking into account the full life
circumstances of the patient. When the deformity causes embarrassment, the
surgical procedure is aimed at achieving psychological as well as physiologic
improvement.
Failure of fusion of the sternal
bands may occur, creating a defect of the anterior chest wall. Separation of
the sternum may be complete or incomplete and may be associated with an ectopia
cordis. When the defect is incomplete, surgical correction of the abnormality
may be accomplished. If the repair cannot be effected by primary
approximation of the sternal segments, a prosthesis or a cartilage autograft
may be used.
Other deformities of the chest wall
occasionally seen include cervical ribs (with or without compression of the
brachial plexus and artery), partial absence of ribs, supernumerary ribs, and
thoracic-pelvic-phalangeal dystrophy.
Respiratory distress may result
from abnormal lung growth caused by restriction by limited rib growth such as
from osteochondrodysplasias (e.g., asphyxiating dystrophy, thanatrophic
dwarfism, upper airway obstruction [diastrophic dysplasia]) or abnormal bone,
cartilage, or collagen development, leading to a small or abnormal thoracic
cage (hypophosphatasia, achondrogenesis, osteogenesis imperfecta).
