Chest Wall Deformities

INTRODUCTION

Pectus excavatum (PE), also known as funnel chest or trichterbrust, is by far the most common disorder of chest wall formation. Approximately 90% of patients with chest wall disorders have PE. The incidence is 1 in 300 live births (Sabiston, 1997). Pectus carinatum (PC), the next most common disorder of the chest wall, is observed in only 7% of patients with chest wall deformities.

PECTUS EXCAVATUM

Controversy exists regarding the indications, timing, and method of repair of PE. Nuss et al introduced a novel and minimally invasive method of repair in 1998. Their technique has intrigued pediatric surgeons and provoked further discussion among members of the pediatric surgical community about the optimal method of repair compared with conventional open repairs (eg, the Ravitch technique).

Embryology/etiology

Several theories exist regarding the cause of PE; however, the etiology remains obscure. PE may be due to overgrowth of costal cartilage, which displaces the sternum posteriorly. Abnormalities of the diaphragm, rickets, or elevated intrauterine pressure are also theorized to cause posterior displacement of the sternum (Brown, 1939; Chin, 1957; Brodkin, 1953; Yamashita, 1987; Falconer, 1990; Lund, 1994). Reports of the coexistence of PE with diaphragmatic agenesis and congenital diaphragmatic hernia support this theory (Falconer, 1990; Grieg, 1990; Lund, 1994). For example, 15% of patients with PE have scoliosis, and 11% have a family history of scoliosis. The coexistence of PE with other musculoskeletal disorders, such as Marfan syndrome and scoliosis suggests that some abnormality of connective tissue may be involved in the development of PE. The fact that 37% of patients have a family history of PE further supports the theory of genetic predisposition (Shamberger, 1988).

Clinical presentation and evaluation

The appearance of PE can range from mild shallow defects to defects in which the sternum almost touches the vertebral bodies. The appearance of the defect is the result of 2 factors: (1) the degree of posterior angulation of the sternum and (2) the posterior angulation of the costal cartilages as they meet the sternum. If additional sternal or cartilaginous asymmetry is present, these defects become challenging for the pediatric surgeon to manage.

PE is generally present at birth, or it arises shortly thereafter. It is often progressive; the depth increases as the patient grows (Shamberger, 1988). PE is more common in male individuals than in female individuals, with a male-to-female ratio is 3:1. PE can be associated with other congenital abnormalities, including diaphragmatic abnormalities. In 2% of patients, it is associated with congenital cardiac anomalies (Shamberger, 1988). In some instances, repair of the PE must occur before the cardiac anomaly is repaired.

Perhaps the most important association of PE is with Marfan syndrome. Approximately 2% of patients with PE have Marfan syndrome; these patients typically have the most severe PE (Shamberger, 1988). Consider the possibility of Marfan syndrome in all patients with severe PE. These patients require a genetic evaluation, ophthalmologic screening for subluxation of the lens, and echocardiography to evaluate for dilatation of the aortic root and mitral valve prolapse. Simple office evaluation for Marfan syndrome includes the thumb test; results are positive if the proximal phalanx of the thumb extends beyond the ulnar border of the palm when the thumb is maximally opposed.

Several methods have been developed to quantitate the severity of PE. These usually involve measuring the distance from the sternum to the spine. Perhaps the most commonly used method is that of Haller et al (1987); this method uses a ratio of the transverse distance to the anteroposterior distance derived from chest CT scans. In the Haller system, a score of 3.25 or higher is associated with a severe defect requiring surgery.

PE generally has no discernible physiologic effect on infants or children. Some children have pain in the area of the sternum or costal cartilage, especially after vigorous exercise. Other children have palpitations that might be related to mitral valve prolapse that commonly occurs with PE. A flow murmur may also be detectible in some patients. This flow murmur is related to the close proximity of the sternum to the pulmonary artery resulting in transmission of a systolic ejection murmur (Guller, 1974).

Asthma is sometimes noted in children with both PE and PC, and an association has been proposed. However, in a review of a large series of patients, asthma was no more frequent in patients than in the general population (Shamberger, 1988). PE also did not seem to affect the clinical course of asthma in patients. It does not appear that any real association exists between the conditions.

The impact of PE on the pulmonary or cardiovascular system continues to be debated. Most studies of pulmonary function fail to show any clinically significant difference, or they show only mild restriction in children at rest or during exercise. In older children and adolescents, a severe pectus deformity has been associated with substantially lowered lung volumes during exercise, but no significant difference was shown at rest (Orzalesi, 1965). Whether low lung volumes at exercise have any important physiologic effect is unknown. In small children, obtaining reliable pulmonary function results is difficult; therefore, any effect that PE has in this age group is unclear.

The impact of PE on cardiac function is similarly unclear. Angiographic studies have shown deformities of the heart as a result of the PE (Garusi, 1964). Exercise studies in patients with PE have shown decreased cardiac output, increased heart rate, and decreased stroke volume in the upright or sitting position (Bevegard, 1962). In the supine position, these parameters improved suggesting that PE limits cardiac filling. Improvement in cardiac function could be demonstrated in many of these patients after surgical repair. Despite these findings, no consistent effect on exercise tolerance has been demonstrated in patients with PE.

Indications for surgery

Several indications for repair of PE exist. Some pediatric surgeons believe that the pectus deformity has little physiologic consequence. One exception may be in the competitive athlete, in whom a slight decrease in exercise tolerance may impair their performance. The major indication is probably psychological. The sunken appearance of the chest wall has been associated with poor self-image in children with PE, especially as they approach adolescence (Einseidel, 1999). Improvement of the appearance of the chest wall after repair improves socialization in these children and adolescents.

Patients with PE sometimes require cardiac or aortic surgery as a result of congenital heart disease or Marfan syndrome; sometimes repair of PE is indicated before surgery. In a review by Shamberger et al (1988), approximately 0.17% of patients with cardiac anomalies also had anterior chest wall deformities. In patients requiring extra cardiac conduits, repair of the PE is recommended before cardiac surgery to avoid external compression on the conduit. One patient underwent repair of the PE at the time of cardiac surgery. This patient subsequently died from intrathoracic bleeding. Therefore, the authors recommended not performing simultaneous cardiac and PE repair. Likewise, repair of PE before aortic surgery in patients with Marfan syndrome may be required to avoid the possibility of extrinsic compression.

SURGICAL REPAIR

Open surgical repair

Meyer performed the first surgical repair of PE in 1911 (Meyer, 1911), followed by Sauerbruch in 1913 (Sauerbruch, 1920). In 1949, Ravitch reported a technique that formed the basis of modern PE surgery until recently. His technique included excision of all deformed cartilage from the perichondrium, division of the xiphoid from the sternum, division of the intercostals bundles from the sternum, and finally transverse sternal osteotomy. The sternum was then displaced anteriorly and held into position by using wires.

In 1958, Welch altered the procedure by preserving the perichondrial sheaths of the costal cartilage. He preserved the upper cartilaginous intercostal bundles and fixed the sternum anteriorly with silk suture. Others further modified the repair by adding a metal strut to ensure stability of the sternum (Rehbein, 1957; Adkins, 1961). Specialists in Japan introduced an interesting modification (Kobayashi, 1997). They used an endoscope to assist in resection of the costal cartilage. Advantages include small surgical incisions and the ability to dissect the pleura under endoscopically magnified visualization.

Haller et al (1970) described a technique of tripod fixation of the sternum. This method uses a posterior sternal osteotomy, subperichondrial resection of the lower deformed cartilage, and oblique division of normal upper second or third cartilage. The obliquely divided cartilages are positioned to override themselves and are secured in an anterior position to the sternum.

A technique developed in France and used primarily in Japan divides the sternum from the cartilage (Wada, 1970). The sternum is then flipped 180° and reattached to the cartilage as a free graft. Because it is not commonly used, this technique has a high complication rate compared with more conventional methods.

Finally, a procedure has been described to correct the deformity by introducing a silicone implant into the subcutaneous space above the sternum (Allen, 1979). This improves the appearance of the defect but does not increase the size of the thoracic cavity.

Outcomes and complication of standard repairs

In general, reports of outcomes and patient satisfaction following the Ravitch (open) repair and variants thereof have been excellent. In several large series, satisfactory results were reported in more than 90% of patients with a metal strut in the repair and in patients without (Hecher, 1981; Willital, 1981). To our knowledge, no direct prospective comparison of the use of metal struts versus no struts in open repairs has been conducted. Haller et al (1970) reported satisfactory results in 100% of 45 patients who underwent their tripod fixation.

Complications of open repair of PE are unusual. The most common complication is a pneumothorax. These tend to be small and can be observed. Large pneumothoraces usually need only aspiration of air. Recurrence occurs in up to 20-30% of patients on long-term follow-up; approximately half of these are recurrences are major events that require a second operation.

The most devastating complication of the open repair is impaired development of the thoracic cavity, thoracic dystrophy occurs most commonly when the surgery is performed in preschool-aged children. Haller (1995) reviewed 12 patients who underwent PE repair and developed thoracic dystrophy. In each instance, repair was performed in children younger than 4 years, and more than 5 ribs were resected. These patients presented with severe exercise intolerance and a clinically significant reduction in pulmonary function. Given their results, Haller et al recommends delaying surgical repair until the patient is older than 6 years and limiting the amount of resected cartilage. The current authors recommend delaying surgery until much of adolescence has occurred (ie, to age 12-16 y).

Minimally invasive repair of PE

In 1998, Donald Nuss et al presented their 10-year results of a new and minimally invasive approach to repairing PE. Their repair was based on the observation that even the chest wall of adults can be remodeled, as seen in adults with barrel chest due to emphysema, without the need for resecting ribs or cartilage. Moreover, remodeling in adults occurs long after the chest wall has matured. Therefore, it should be possible to remodel the chest wall in children without the need for cartilaginous resection or sternal osteotomies. The other key observation was based on the management of orthopedic conditions, such as scoliosis and club foot. These conditions can be corrected conservatively by placing splints and leaving them in place for long periods.

Minimally invasive repair of PE (ie, the Nuss procedure) involves inserting a custom bent curved metal bar underneath the sternum through lateral chest incisions. The bar is then turned placing the convexity of the bar upward and instantly correcting the pectus depression. The bar is then secured to the lateral aspect of the chest wall and/or ribs and left in place for 2-3 years, after which it is removed in an outpatient procedure.

Outcome of the Nuss procedure

In 2000, Hebra et al surveyed pediatric surgeons in the American Pediatric Surgical Association (APSA) membership to determine outcomes and complications of the Nuss procedure in a large sample of patients. Of 74 responders, 42% used the Nuss procedure as their primary method of repair in 251 cases overall. A complication rate of 21% was reported. This rate is somewhat lower than that in 2 other series (Nuss, 1998; Molik, 2001); however, it is high compared with the <10% complication rates in several large series of open pectus repairs. The most common complication was bar displacement (9.2%), followed by pneumothorax requiring a chest tube (4.8%). Pneumothorax is a common complication and occurred in all series. In general, the pneumothoraces were small and resolved spontaneously. In Nuss' series, only 1 patient required a chest tube to manage a pneumothorax.

The APSA survey also showed a substantial reoperation rate with the Nuss procedure. The most common reason for reoperation was bar displacement. Reoperation was required in only 2 patients in Nuss' series; both were for bar displacement. The recent introduction of a lateral stabilizing device may decrease the incidence of bar movement.

Few serious complications have been reported with minimally invasive pectus repair (Hebra, 2000; Molik, 2001). One cardiac perforation occurred in an 8-year-old child who had a moderately deep and asymmetric deformity. The child required a median sternotomy; emergency heart-lung bypass; and repair of the right atrium, tricuspid valve, and left ventricle. At 2-year follow-up, the child was doing well. One case of bilateral empyema with pericarditis has also occurred. In this case, bilateral chest debridement and open pericardial debridement was performed. Three cases of thoracic outlet syndrome are reported. At the time of the report, the bar had to be removed in 1 patient because of severe symptoms referable to the brachial plexus and arm cyanosis that was relieved with arm elevation. The other patients had a gradual improvement of symptoms and still had the bar in place.

The present authors know of no reported cases of thoracic dystrophy after the Nuss procedure. Haller et al (1995) found this complication primarily in younger patients. In the series Nuss et al presented, 19 patients were aged 5 years or younger when they underwent PE repair. None were reported to develop thoracic dystrophy. In general, no conclusions can be made from the other series. Surgeons Hebra et al polled did not report thoracic dystrophy, presumably because the growth plates are not injured or removed in the Nuss procedure compared with the classic Ravitch procedure. However, the patients' ages and the lengths of follow-up are unknown. Therefore, though preliminary indications suggest that thoracic dystrophy may not be a complication in the Nuss procedure, this suggesting has not been confirmed. Long-term follow-up of the youngest patients is required.

Determining acceptable cosmetic outcomes is subjective. Nuss reported good-to-excellent outcomes in 26 of 30 patients after bar removal. Most surgeons Hebra et al polled considered cosmetic outcomes to be good or excellent in 96.5% of patients. However, in this poll, the length of follow-up and the number of patients who achieved bar removal are unknown. Because PE can recur even 5-10 years after open repair, follow-up longer than that currently available with the Nuss procedure is needed to determine the durability and cosmetically acceptability of this method of repair. Also, whether teenagers derive the same cosmetic benefit as younger children is unclear. Few patients in Nuss' series (the series with by far the longest follow-up) were teenagers. In contrast, 3 other series of patients involved older children (mean age, 6.8 y vs 12.3, 9.5, or 11.5 y).

At present, no information exists regarding the physiologic benefit of the minimally invasive approach to PE repair. As discussed previously, it is difficult to reliably demonstrate any cardiopulmonary deficit in patients with PE. In open repairs, several studies have been performed comparing cardiopulmonary effects before and after repair. In his review of the subject, Shamberger (2000) found no consistent evidence that open PE repair provided any cardiopulmonary benefit. In fact, several studies have demonstrated worsening of pulmonary function after repair, perhaps as a result of increased chest wall rigidity from the surgery. In contrast, studies assessing workload and exercise tolerance often show improvement after PE repair. Therefore, the cardiopulmonary benefit of open PE repair is, at best, uncertain. It will be interesting to see what affect, if any, the minimally invasive repair will have long-term.

Without the need for cartilage resection and sternal osteotomy, one might expect decreased postoperative rigidity of chest wall and an increased likelihood of improvement in pulmonary function. Borowitz et al compared preoperative and postoperative pulmonary function in 10 patients undergoing the Nuss procedure. They found no significant difference in preoperative function to that 1-year postoperatively with the bar in. Therefore, having the bar in place has no detrimental effect on pulmonary function. The effect after bar removal remains to be seen.

Modifications to the Nuss procedure

Several modifications to the Nuss procedure have been proposed to avoid the complications discussed above. Implementation of a lateral stabilizing bar was perhaps the first major modification and was a response to a substantial number of bar displacements. Other surgeons have used somewhat different modifications to combat bar displacement. Hebra et al (2001) recently propose the use of a 3-point fixation method in conjunction with the stabilizing bar. In this technique, a stitch is placed around a rib and bar adjacent to the sternum with the aid of thoracoscopy. In 20 patients undergoing the Nuss procedure with the 3-point fixation modification, only 1 bar displacement (5%) was noted in 1-year follow-up. In the affected patient, an absorbable suture was inadvertently used.

Another recent modification is the use of thoracoscopy to monitor safe passage of the clamp across the mediastinum. Thoracoscopy came into widespread use after report of the cardiac injury discussed above. A survey of surgeons performing the Nuss showed that 61% now use thoracoscopy on a routine basis (Hebra, 2000). Miller et al (2001) describe a separate variation in which a subxiphoid incision is made through which a subxiphoid tunnel is created into the anterior mediastinum. This technique allows direct visualization of the bar as it passes under the sternum.

Recommendations for the length of time before bar removal also have been changed. In the original description of the operation, the bar was left in for 2 years. Authors have recently recommended increasing that time to 3 years to decrease the incidence of PE recurrence. Whether this prolongation will increase the number of positive outcomes has not been determined.

Because of the variety of modifications, it can be difficult to compare results from 1 series to the next. An attempt is now underway to formulate a prospective study comparing the Nuss procedure to open repair. That study should answer many questions. However, unless the use of modifications to both the Nuss procedure and the open operation are carefully controlled, the use of such a prospective study may be limited.

PC AND OTHER RARE DEFORMITIES OF THE ANTERIOR CHEST WALL

Introduction

Pigeon chest (PC) is the second most common congenital deformity of the chest wall. PC constitutes approximately 7% of all anterior chest wall deformities. It is more common in boys than girls (ratio, 4:1). It typically is apparent at birth and tends to worsen as the child grows. PC is typically thought of as a protrusion of the chest wall (the opposite of PE), but it represents a spectrum of deformities involving the costochondral cartilage and sternum. Costochondral cartilage involvement may be unilateral or bilateral. In addition, the sternal protrusion may be superior or inferior. The defect may be asymmetrical, causing a rotation of the sternum with depression on 1 side and protrusion on the other.

Etiology

The pathogenesis of PC, much like that of PE, is obscure. PC has been postulated to represent an overgrowth of ribs or costochondral cartilage. A genetic predilection may exist because 26% of patients have a family history of chest wall deformity. Furthermore, a strong association with scoliosis implies a connective tissue disorder.

Presentation

PC deformity can be broken down into 3 distinct types of deformities. The first is termed chondrogladiolar protuberance and is characterized by a symmetric protrusion of the body of the sternum (gladiolus) and costal cartilages. A lateral depression of the ribs results, which is known as runnels or Harrison grooves. Chondrogladiolar protuberance, which makes up 90% of PC deformities, has been described as looking like the result of a giant hand crushing the chest from each side.

The second class of deformities includes the asymmetric forms, which make up approximately 9% of PC. This group is characterized by protrusion on 1 side and normal position on the other (ie, keel deformity) or by protrusion on 1 side and depression on the other. The least common form, chondromanubrial protrusion, makes up less than 1% of all cases of PC. It results from protrusion of the manubrium and relative depression of the body of the sternum. Chondromanubrial protrusion is alternatively known as pouter PC, arcuate deformity, manubriosternal prominence, and Currarino-Silverman syndrome. The series of patients described by Currarino and Silverman noted absence of sternal sutures and obliteration of the sternomanubrial junction creating a shieldlike sternum. They also noted a high association with congenital heart disease (20%).

Treatment

The treatment of PC is surgical, though successful applications have been reported of orthotic bracing to correct deformities in younger children. Ravitch reported the first surgical repair in 1952. He described a method in which resection of abnormal cartilage was combined with double osteotomy of the sternum. Other surgical attempts at repair were described in which part of the sternum was resected up to and including a complete subperichondrial resection.

The modern method of repair is based on the procedure described by Ravitch and Vos in 1973. They performed subperichondrial resection of the abnormal cartilage and preserved the sternum. Transverse osteotomy of the sternum was made and, combined with fracture of the posterior cortex of the sternum, allowed posterior displacement of the sternum. In 1987, Shamberger and Welch (1987) published their experience with this repair in 152 patients. Satisfactory results were achieved in all but 3 patients (98%).

Complications

In general complication rates for the Welch technique are low. In a series of 152 patients Shamberger and Welch (1987) reported, the complication rate was only 3.2%. The most common complication was pneumothorax. Rates of blood loss were low, and only 5 transfusions were required in this series of patient. Recurrence was limited to the patients who undergo operation before full maturity and who have inadequate resection of cartilage. This is particularly true in patients with an asymmetric deformity in whom only unilateral resection of cartilage is performed. The growth of the nonresected side often tilts the sternum to the uninvolved side, resulting in an even worse deformity. In another series of patients, no recurrences in young patients were noted (Welch, 1958).

POLAND SYNDROME

Poland syndrome, named after Albert Poland who first described this entity while attending medical school, refers to a spectrum of disorders involving hypoplasia of the chest wall. This may involve, alone or in combination, the pectoralis major, pectoralis minor, serratus anterior, ribs, and soft tissue. Deformities of the arm and hand may also be observed.

The incidence of Poland syndrome is approximately one in 32,000 live births, and its occurrence is almost always sporadic or nonfamilial. It is 3 times more common in boys than in girls and involves the right side in 75% of patients. Multiple theories regarding the etiology have been proposed and include abnormal migration of embryonic tissue, hypoplasia of the subclavian artery or in utero injury from attempted abortion. However, none of these are widely believed

Rare associations of Poland syndrome with other diseases have been noted. Leukemia has been observed in some patients with Poland syndrome. An association with Mobius syndrome also has been reported. Mobius syndrome involves unilateral or bilateral facial palsy and abducens oculi palsy.

The presentation of patients with Poland syndrome varies according to the type of defect. In patients with notable bony defects, lung herniation may be noted early in childhood, especially with coughing or crying. Some patients may have a functional flail chest and present with respiratory compromise. The lung itself is otherwise normal in these patients. In patients with significant muscular and soft tissue involvement, Poland syndrome may become evident secondary to exercise intolerance. However, patients usually present with cosmetic complaints.

Treatment of patients with Poland syndrome depends on the type of defect. Those with rib aplasia require reconstruction of the chest wall. Ravitch first described the reconstruction of the chest wall with autologous rib graft in 1966, and this remains the standard repair. The

repair involves exposure of then chest wall through a transverse incision as in repair of a pectus. Subperichondrial rib resection is performed on both sides with care taken not to violate the pleural cavity. The third, fourth, and fifth costal cartilages are removed in their entirety, whereas the sixth and seventh are resected to the point where they join the costal arch. A transverse osteotomy through the sternum is performed and to allow correction of the sternal rotation. Rib grafts taken from the contralateral fifth or sixth rib are used to reconstruct the chest in patients with rib aplasia.

Breast reconstruction is often required in female patients. Techniques include implants and latissimus dorsi flaps, often in conjunction. Reconstruction is performed after puberty to optimize the match between the normal and reconstructed breast.

Outcomes of surgical correction of Poland syndrome depend on the type of defect and the expectation of the patient. Some variants of Poland syndrome, such as diffuse rib aplasia without depression, are not surgically correctable at all. Therefore, patients should be

carefully counseled before surgery.

JEUNE SYNDROME

Jeune syndrome, or asphyxiating thoracic dystrophy, is a failure of chest wall growth in utero resulting in a narrow chest cavity and pulmonary hypoplasia. In 1954, Jeune et al first described the syndrome in a newborn. Patients with this syndrome typically die at birth, though many cases are being recognized with prolonged survival.

Jeune syndrome is inherited in an autosomal recessive pattern, and no chromosomal abnormalities have been seen in association with it. The pattern of expression and the degree of pulmonary hypoplasia are variable, which accounts for the longevity in certain patients.

At present, no adequate treatment exists for this syndrome. Multiple attempts have been made to devise a means of surgically enlarging the thoracic cavity; however, these have generally been unsuccessful.

An acquired form of thoracic dystrophy has been recently recognized as a complication of PE repair in young children. Reports of operative chest expansion in this group of patients have demonstrated encouraging short-term results.

STERNAL DEFECTS

Sternal defects can be categorized into 4 types, all of which are rare: thoracic ectopia cordis, cervical ectopia cordis, thoracoabdominal ectopia cordis, and cleft sternum. Thoracic ectopia cordis, or naked heart, is the result of failure of somatic structures to form over the heart, leaving it completely exposed. The sternal anomalies run a spectrum from being completely split to being almost completely intact with a central defect. Thesurvival rate of patients with thoracic ectopia cordis historically has been poor. Only 3 successful repairs in 29 attempts have been described.

Cervical ectopia cordis differs from thoracic ectopia cordis by the amount of superior displacement of the heart. Craniofacial abnormalities are often present and extremely

severe; they can include fusion of the apex of the heart to the mouth. No survivors or successful repairs have yet been documented.

Patients with thoracoabdominal ectopia cordis have an inferiorly displaced heart underlying an inferiorly cleft sternum. The heart is covered by membrane or thin skin. Inferior displacement of the heart results from a semilunar defect in the pericardium and diaphragm. Abdominal wall defects are also common. This association of cardiac, pericardial, diaphragmatic, abdominal wall, and sternal defects is also referred to as Cantrell pentalogy. Surgical repair of thoracoabdominal ectopic cordis has been successful compared to the other forms of ectopic cordis.

Cleft sternum is the least severe of the 4 anomalies because the heart is covered and is in a normal position. Overlying the heart is a partially or completely cleft sternum; partial split is more common than complete split. Several associations are seen with cleft sternum, but cardiac defects are rare. A bandlike scar often extends from the sternum to the umbilicus or superiorly to the neck is seen. Hemangiomas of the head and neck can also be found.

In most infants, cleft sternum usually does not cause any detectable symptoms. On occasion, respiratory symptoms result from the paradoxical motion of the sternal defect. The primary indication for repair is to protect the heart. Repair is performed through a midline incision, and the 2 halves of the sternum are approximated with nonabsorbable suture. In incompletely cleft sternums, a wedge of cartilage is sometimes removed from the base of the cleft to facilitate approximation. Repair is best performed in infants because the chest wall is most pliable