Pectus Excavatum

In pectus excavatum, the growth of bone and cartilage in the anterior chest wall is abnormal, typically affecting 4-5 ribs on each side of the sternum. The appearance of the defect widely varies, from mild to very severe cases, and some patients present with significant asymmetry between the right and left sides. The exact mechanism involved in this abnormal bone and cartilage overgrowth is not known, and, to date, no known genetic defect is directly responsible for the development of pectus excavatum. Despite the lack of an identifiable genetic marker, the familial occurrence of pectus deformity is reported in 35% of cases. Moreover, the condition is associated with Marfan syndrome and Poland syndrome.

The cause of pectus excavatum is unknown. It probably originates from a genetic defect that results in abnormal musculoskeletal growth. The cartilaginous portion of the rib is very likely the main source of this abnormal growth pattern. Abnormalities of rib morphogenesis and growth are the most likely causes of pectus excavatum and pectus carinatum. In pectus excavatum, the sternum is thought to be pushed in by abnormal growth at the articulation with the ribs and cartilage. Again, the exact mechanism that results in this abnormal growth pattern is not known. Increased work of breathing, as is observed in young patients during exercise or play activity, may contribute to the progression of the pectus deformity, particularly during early the teenage years. However, no scientific evidence supports such a theory.

United States statistics

Pectus excavatum occurs in an estimated 1 in 300-400 births, with male predominance (male-to-female ratio of 3:1). Pectus excavatum comprises approximately 90% of all chest wall deformities.

International statistics

Although limited data are available, international frequency is probably the same as that reported in the United States. However, in certain countries (eg, Argentina), pectus carinatum is more common than pectus excavatum.

Race-, sex-, and age-related demographics

Pectus excavatum appears to be most prevalent in whites. Unfortunately, no specific data are available regarding racial distribution; however, clinical observation indicates that treating pectus excavatum in African Americans is unusual.

The male-to-female ratio is 3:1. Despite such observation, no known genetic factor linked to the X or Y chromosome has been reported.

Most cases of severe pectus excavatum are noticed at birth, with progressive worsening of the child's growth and development. More than 80% of all cases are identified within the first 1-2 years of life. The condition typically becomes much more pronounced at puberty, during the time of rapid bone and cartilage growth. Most patients are brought to medical attention during their teenage years because of the significant change in the appearance of their chest.

The prognosis of pectus excavatum, with treatment, is excellent. Patients with mild pectus excavatum who do not undergo operative correction also have an excellent prognosis. Patients with moderate-to-severe pectus excavatum may experience problems related to cardiopulmonary impairment, decreased exercise tolerance, decreased stamina, and adjustment disorders related to the impact of this deformity on body image and coping mechanisms. Mortality is not associated with the condition.

A prospective study by Lomholt et al indicated that physical and psychosocial health-related quality of life (HRQL) improves in children following surgery for pectus excavatum. Results were based on patient and parent replies to the Child Health Questionnaire provided preoperatively and at 3 and 6 months following correction of the condition. Increased emotional well-being and self-esteem and greater participation in physical and social activities were reported postoperatively. ^[1]

A literature review by Maagaard and Heiberg found that patients who underwent correction of pectus excavatum have frequently reported a postoperative increase in exercise stamina, with the outcome apparently unrelated to the specific surgical approach used. The investigators suggested that greater exercise capacity results from an increase in anterior-posterior thoracic dimensions, relieving pressure on the cardiac chambers and, consequently, allowing better filling of the heart. ^[2]

Morbidity/mortality

Many patients with pectus excavatum are asymptomatic from a functional standpoint. The degree of cardiopulmonary impairment caused by lung compression and the level of cardiac displacement that results from the caved-in chest are subjects of controversy. Exercise tolerance is frequently reported as abnormal, and a restrictive pattern in pulmonary function test can be identified in severe cases. Cardiac function is usually normal, but mitral valve prolapse has been reported in 20-60% of cases. Echocardiography typically reveals some degree of atrial compression and cardiac displacement. Rarely, it may reveal mitral or tricuspid regurgitation. Echocardiographic analysis has demonstrated improved cardiac index upon exertion after operative repair of the deformity. The long-term health risks of patients who are managed without surgery are not known.

Complications of surgery

There are few large series that examined complications and outcomes of the minimally invasive technique for repair of pectus excavatum (MIRPE). ^{[3, 4]}  In those reports, patient and family satisfaction were found to be very good, with excellent and good results reported at 93% and 96%, respectively. Other studies that evaluated short- and long-term outcomes after MIRPE also reported excellent and good results in more than 90% of cases. ^{[5, 6]} However, one multi-institutional study, which reviewed 251 cases of MIRPE, demonstrated a significant rate of complications (the overall incidence rate of complications was almost 20%). ^[4] ​

By far, the most common complication reported requiring reoperation was displacement of the retrosternal stainless steel support bar (initially reported to occur in 9.5% of all patients). Such displacement can include a 90° rotation, a 180° rotation, or a lateral migration. Teenaged patients are at higher risk for complications, particularly pectus bar displacement, probably because of the increased pressure on the bar generated by a larger chest and more rigid chest cage. Today, the risk of bar displacement has been reduced to approximately 2.5% owing to new techniques of bar stabilization (described under Surgical technique in Surgical Care).

The acceptance and popularity of MIRPE developed quickly since its introduction in 1997. The principal advantages of this new technique are based on the fact that incising the anterior chest wall, raising the pectoralis muscle flaps, resecting the rib cartilages, and performing a sternal osteotomy are not needed. This leads to a much shorter operating time, minimal blood loss, and early return to full activity because the stability and strength of the chest wall is not compromised. The apparent simplicity of the technique, combined with the early good results reported, contributed to the enthusiastic widespread use of this operation by many pediatric surgeons.

Unfortunately, a relatively high rate of complications was reported when many different surgeons performed the operation, probably reflecting the learning curve associated with the introduction of this new technique. Since the first MIRPE was performed, the bar has been modified 4 times and is now strong enough to withstand the pressure of even the most severe deformity. The poor results likely occurred early in the reported series because the bar was too soft, was removed too soon, or was not stabilized adequately. Experience has shown that stabilization of the bar is absolutely essential for success, and the use of a lateral stabilizing bar and the third point of fixation (when appropriate) minimizes the occurrence of bar displacement.

An interesting observation has been that complications, mainly bar displacement, have appeared to be more common in teenaged patients. Initially, the MIRPE was limited to the younger prepubertal patients (aged 3-12 y), which probably accounted for the rare occurrence of bar displacement in the first report by Nuss. ^[7]  Older patients were offered the procedure because of the success of the procedure in young patients. Only later was the importance of proper stabilization of the bar identified and the lateral stabilizing bar was introduced (in 1998), followed by the addition of the third point of fixation technique (in 2000) to provide additional support and stability for the bar. The results seemed to have improved so much that the operation is now considered in adult patients with pectus excavatum.

Fortunately, most factors that may lead to complications and poor results were related to early inexperience, and these factors have been corrected. Moreover, the introduction of thoracoscopy when performing MIRPE has significantly enhanced the surgeon's ability to pass the bar precisely behind the sternum, avoiding the risk of cardiac or vascular injury. Reassuringly, one reported case of cardiac perforation occurred prior to the routine use of thoracoscopy.

Mortality of surgery

There have been at least 2 reported cases of cardiac injury and death following the Nuss procedure. The retrosternal dissection during the MIRPE and the placement of the bar can certainly cause a life-threatening complication such as cardiac injury. Becmeur et al published a retrospective review of 16 cases of cardiac lacerations. ^[8]  It is important for surgeons, patients, and their families to be aware of this risk. Meticulous attention to surgical technique as outlined in this article is important to minimize the risk of cardiac injury.

Because of the recent advances in the operative repair of pectus excavatum, education of medical professionals and the public is important. Again, patients with pectus excavatum should be referred to a surgeon experienced in the field of congenital chest wall malformations. Early assessment and follow-up is essential to maximize good outcomes.

After operative repair of the pectus excavatum, instruct patients on correct posture to eliminate musculoskeletal pain and to prevent worsening of the spinal deformity. Emphasize that repair of the pectus in itself does not result in correction of any associated spinal deformity or problems related to poor posture.