What is Pectus Excavatum?
Pectus excavatum, also known as sunken or funnel chest is a congenital chest wall malformation in which several ribs and the sternum grow abnormally, producing a Pectus excavatum occurs in an estimated 1 in 300-500 births, with a male predominance (male-to-female ratio, 3:1). The condition is typically noticed at birth, and more than two-thirds of cases are diagnosed within the first year of life. Worsening of the chest’s appearance and the onset of symptoms are usually reported during rapid bone growth seen in puberty and early teenage years. Many patients are not brought to the attention of a pediatric surgeon until the patient and the family have noticed such changes. Despite the lack of an identifiable genetic marker, the familial occurrence of pectus deformity is reported in 35% of cases. concave or caved-in appearance of the anterior chest wall and sternum.
The Nuss Procedure: is an operative technique known as minimally invasive repair of pectus excavatum (MIRPE). It was originally described by Donald Nuss and this is why it is also called the Nuss technique or pectus bar procedure. Nuss performed the first minimally invasive operation for the correction of pectus excavatum in the 1980s, but it was not until 1997 that this innovative technique was introduced to the American Pediatric Surgical Association.
Because of the early excellent results of the Nuss procedure and because of its less radical nature, the popularity of this operation has grown dramatically and it is still growing
What Are The Exact Indications That a Person May Need a Nuss Procedure Done?
Pectus excavatum patients are considered candidates for corrective surgery based on the following criteria:
- Severity of the deformity (as determined by measurement of the chest Haller index)
- Resulting functional impairment
- Psychosocial impact of the deformity on the patient.
The chest Haller index is a measurement taken from a non-contrast CT scan of the chest in which a ratio is obtained between the lateral and anterior-posterior diameter of the chest wall at the point of maximal depression of the sternum. A normal chest index is around 2.5. Patients with an index greater than 3.2 have a fairly pronounced and severe pectus excavatum and will typically benefit from operative correction. Even if asymptomatic, those patients usually benefit from the corrective surgery.
Of note, obtaining a chest Haller index in a young patient with pectus excavatum is not necessary. The Haller index should be obtained before corrective surgery (within months and not years) so that it can offer information helpful to the surgeon in planning the operative correction of the pectus.
Symptomatic patients with pectus excavatum typically experience occasional episodes of chest pain, shortness of breath with exertion, and decreased exercise tolerance. Such patients usually have abnormal pulmonary function test results, and echocardiography may demonstrate mitral and tricuspid valve regurgitation. Mitral valve prolapse is also commonly seen on the echocardiogram.
Many patients with mild-to-moderate pectus excavatum do not report any significant shortness of breath. Upon further questioning, however, one may find that the child is unable to keep up with their peers during play and physical activity. They usually report getting tired more easily.
Another common observation in children with pectus excavatum is that they are very shy and reserved about their physical appearance. Frequently, as summer comes around, they are unwilling to take their shirt off for sports, swimming, or around other children. The psychosocial stress caused by the abnormal chest can be quite severe and can result in a major adjustment disorder, depression, and even suicide ideation later in life.
The most common goal in the operative repair of pectus excavatum is to correct the chest deformity. As noted above, this is particularly important in teenagers, in whom the abnormal appearance of the chest can result in significant problems related to body image and self-esteem. Thus, the desire to improve the appearance of the chest is considered an appropriate medical indication for surgery.
The current recommendations support the use of MIRPE in patients aged 5-20 years. The ideal age for undergoing this operation has been established at 8-12 years because, in this age range, the chest wall is still very malleable, stabilization of the bar is easily achieved, thoracic epidural can be safely placed, and the child is mature enough to understand the operation and postoperative instructions, particularly incentive spirometry, which is essential for minimizing pulmonary problems after surgery.
Of note, operative correction of pectus excavatum should not be viewed as an operation limited exclusively to pediatric patients. Indeed, the open technique has been used in adult patients with excellent results. Although experience with MIRPE in adult patients has been relatively limited, there is increasing evidence to suggest that similar principles apply to adult patients and that operative correction using MIRPE can be achieved in this population.
Limiting factors for MIRPE in adults include a larger chest wall and poor malleability of the ribs, cartilage, and sternum. A surgeon experienced in the field of chest wall malformations must carefully evaluate adult patients to determine which operation would best correct the anatomical deformity.
Moreover, adult patients with pectus excavatum who undergo open-heart surgery have significant displacement and rotation of the heart to the left chest. This can make the operative approach to the heart at the time of open-heart surgery very challenging. With this in mind, elective repair of the pectus deformity prior to open-heart surgery may be indicated in selected adult cases.
In a retrospective multicenter study of 20 adult patients with recurrent pectus excavatum, Kocher et al found MIRPE to be safe and effective for repairing the recurrences after a failed Ravitch procedure. The results were good-to-excellent in the majority of adults, and there were no major complications or further recurrences
Technical Considerations For Nuss Procedure:
Not all patients with pectus excavatum are considered candidates for corrective surgery. The decision to undergo surgery is based on clinical symptoms and the severity of the deformity. The surgeon, patient, and immediate family must reach a consensus as to the benefits of operative repair for the child with pectus excavatum. The morbidity and mortality of the surgical intervention must be taken into consideration.
Patients must be selected carefully for the procedure. Preoperative assessment may include pulmonary function testing (PFT) and contrast computed tomography (CT) of the chest. CT allows determination of the preoperative Haller index (as previously described). Patients with a Haller index greater than 3.2 are considered candidates for the minimally invasive repair. PFT typically demonstrates mild changes in pulmonary volumes (restrictive pattern). Echocardiography is performed selectively in patients with clinical evidence of Marfan syndrome or with any cardiac symptoms or murmurs.
Appropriate patient selection and careful attention to operative and technical details minimize the risk of complications. Moreover, recognizing that the ideal age for operative repair is between 8 and 12 years of age is important. Prepubertal patients have a more flexible rib cage, which facilitates reconstruction and remodeling of the ribs and sternum. Younger patients typically experience less postoperative pain and discomfort than teenagers and young adults do.
Few studies have been done and published that are evaluating the short and long-term outcomes of patients following minimally invasive repair of pectus excavatum. The overall patient and family satisfaction have been considered very good, with excellent and good results reported in more than 90% of cases.
In 2000, a multi-institutional study that reviewed 251 MIRPE cases demonstrated a significant complication rate (overall incidence of complications was almost 20%). The most common complication necessitating reoperation was displacement of the retrosternal stainless steel support bar (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 a more rigid chest cage.
The rate of complications was found to be relatively high when many different surgeons performed the operation. This probably reflects the learning curve associated with the introduction of MIRPE. Since the first such procedure was performed, the bar has been modified four times; current bars are strong enough to withstand the pressure of even the most severe deformity.
Factors contributing to the results reported include the softness of the bars initially used, the premature removal of the bar, and the failure to stabilize the bar adequately. Experience has shown that stabilization of the bar is absolutely essential for success and that the use of a lateral stabilizing bar and the third point of fixation (when appropriate) can minimize the occurrence of bar displacement.
The spectrum of adverse outcomes is variable, and most complications are considered rare and unusual. The following is a list of reported complications after MIRPE (and their estimated incidence):
- Pectus bar displacement requiring reoperation (2.5%)
- Pneumothorax necessitating chest tube (3%)
- Overcorrection (3%)
- Epidural catheter complications (4%)
- Bar allergy (1-2%)
- Wound infection (1%)
- Pleural effusion (1%)
- Thoracic outlet syndrome (<0.5%)
- Pericarditis (<0.5%)
- Cardiac injury (<0.5%)
- Sternal erosion (<0.5%)
- Death (<0.2%)
With respect to cardiopulmonary outcomes after MIRPE, a study has demonstrated that objective measures of forced expiratory volume in 1 second (FEV1), total lung capacity, diffusing lung capacity, and respiratory quotient all showed significant improvement (after bar removal) in comparison with preoperative values, whereas normalized values of cardiac index at rest did not.
It should be noted that this improvement in cardiopulmonary function is not necessarily seen during the time that the support bar is still in place. For that reason, functional outcomes should not be evaluated until the patient has completed treatment with bar removal. Of note, the dreaded complication of chest wall constriction after Ravitch repair of pectus excavatum has never been reported with the Nuss procedure.
Attempts have been made to determine which technique (ie, MIRPE or open surgery) provides the better outcome in patients with pectus excavatum. Although many surgeons with expertise in the management of children with chest wall deformities have shown some bias toward the use of the Nuss technique, this bias is not strongly supported by prospective randomized published data.
A systematic review by Johnson et al compared outcome measures for Nuss and Ravitch procedures (as well as other, less common approaches) in both pediatric and adult patients. The results indicated slightly better outcomes with the Nuss procedure than with any other approach in children; in adults, the results did not lead to a preference for the Nuss procedure over the Ravitch procedure or vice versa, though both were preferred over the less common approaches.
Since the introduction of thoracoscopy and lateral stabilizers, as well as the third point of fixation technique, bar displacement has become quite unlikely, with an estimated incidence of less than 2.5%.
Another significant advantage of MIRPE over the open surgical procedure is that the dreaded complication of “thoracic constriction” (Jeune syndrome) does not seem to occur with this new technique. Chest wall constriction has been described in a few patients following extensive open pectus excavatum operations. Apparently, the bone growth center can be affected, which results in restriction of chest wall growth with marked limitation of ventilatory function. Such patients are very symptomatic and cannot compete in running games. The forced vital capacity and FEV1 are typically decreased by more than 50% of predicted reference range levels.
With MIRPE, because no resection or incision is made on ribs or cartilages, such a complication does not appear to be a problem. Once the cartilage and bony structures are remodeled, normal or improved pulmonary function is established and the flexibility and malleability of the chest remain unaffected.
Critics of MIRPE claim that it is too invasive, poses substantial risks and is not pain-free. Proponents argue that MIRPE, compared with open surgery (modified Ravitch operation), eliminates the need for an anterior chest wall incision with the creation of pectoralis muscle flaps, resection of several ribs and cartilages, and sternal osteotomies. MIRPE allows a much shorter operating time, causes minimal blood loss, and results in minimal surgical chest wall scarring. Moreover, the stability and strength of the chest wall are not compromised, as is sometimes the case with open repair.
Data published in 2011 by the multicenter study group evaluating the pulmonary functional outcome of pediatric patients with pectus excavatum treated with MIRPE clearly demonstrated that the increasing severity of pectus excavatum is associated with reduced pulmonary function and that the Nuss operation can effectively reverse that process.
Final data analysis generated by the multicenter study and published in 2013 clearly demonstrated that there is a significant improvement in lung function at rest and in VO2 max and O2 pulse oximetry after surgical correction of pectus excavatum with a CT index greater than 3.2. The study concluded that operative correction significantly reduces the CT index and markedly improves the shape of the entire chest and cardiopulmonary function.
Patient Education and Consent:
All patients should avoid all oral intake (nil per os [NPO]) for 12 hours before general anesthesia. Gentle bowel preparation with magnesium citrate might be of benefit in older patients, in that postoperative constipation is quite common after discharge from the hospital, primarily because the patients have taken large amounts of narcotics that will predispose them to constipation.
Elements of informed consent
The informed consent should include a discussion of the treatment options, including nonoperative management, minimally invasive repair, and open surgery. Short and long-term outcomes should be discussed with the patient and caregivers/parents. The risks, morbidity, and mortality must be discussed.
The most common complication (bar displacement) and the possible need for preoperative surgery must be discussed. Although rare, the possibility of death must be discussed. Patients with an asymmetric pectus excavatum must be made aware that the asymmetry of the chest may continue despite successful repair of the caved-in sternum.
Monitoring & Follow-up:
Intraoperative monitoring typically includes standard anesthetic monitoring and pulse oximetry. Placing an arterial line and/or central line for hemodynamic monitoring is not necessary. Due to the presence of the thoracic epidural and high use of postoperative narcotics, having patients monitored in a critical care unit (such as a pediatric intensive care unit [PICU] or step-down unit) after the procedure might be necessary because of the risk of postoperative respiratory depression.
The patient is discharged home once the pain is adequately controlled with oral medications. The average length of stay is 4-7 days. Good posture with a straight back is very important, even after discharge.
Once at home, the patient may sleep in any position that is comfortable. Again, bending at the hip and slouching are discouraged, particularly in the first month. Regular activity is permitted as pain reduces and mobility increases. Heavy lifting is not permitted for 1 month after surgery.
A physical fitness program should be started 30 days after corrective surgery in order to promote healing and remodeling of the chest wall. Contact sports should be avoided for at least 6 months, particularly in older children and teenagers; a direct blow to the chest may predispose the patient to bar displacement.