Nuss Procedure for 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 concave or caved-in appearance of the anterior chest wall and sternum. (See the image below.)

Typical appearance of (A) teenaged boy with severe pectus excavatum and (B) young girl with pectus deformity.

View Media Gallery

Pectus excavatum occurs in an estimated one in 300-500 births, with a 3:1 male predominance. 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. ^[1] 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. ^[2]

This topic focuses on the operative technique known as minimally invasive repair of pectus excavatum (MIRPE). It was originally described by Donald Nuss and thus is also known as 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 and subsequently published in the Journal of Pediatric Surgery. ^[3]

Because of the early excellent results of the Nuss procedure and because of its less radical nature (as compared with the open Ravitch technique), ^{[4, 5, 6, 7]} the popularity of this operation has grown dramatically. ^[8]  (See the image below.)

Nuss procedure. Appearance of chest before (above) and after (below) Nuss operation for pectus excavatum. Image illustrates cosmetic advantage of minimally invasive approach.

View Media Gallery

Pectus excavatum patients are considered candidates for corrective surgery on the basis of 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 noncontrast computed tomography (CT) scan of the chest in which a ratio is obtained between the lateral and the anterior-posterior diameter of the chest wall at the point of maximal depression of the sternum (see the image below). 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. ^[9] Even if asymptomatic, those patients usually benefit from the corrective surgery.

Noncontrast chest CT scan of patient with pectus excavatum. Chest Haller index is ratio of lateral (transverse) diameter of chest wall to anteroposterior diameter at point of maximal depression of sternum.

View Media Gallery

Of note, obtaining a chest Haller index in a young patient (see the image below) with pectus excavatum is not necessary. The Haller index should be obtained before corrective surgery (within months and not years) so that it can provide information helpful to the surgeon in planning the operative correction of the pectus. ^{[10, 11]}

Young infant with pectus excavatum.

View Media Gallery

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. ^{[12, 13]}

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 children are unable to keep up with their peers during play and physical activity. ^[14] They children 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. ^{[15, 16]}

The most common goal in operative repair of pectus excavatum is to correct the chest deformity. As noted above, this is particularly important with 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. ^[17]

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. ^[18]

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 not been as extensive, ^[19]  there is evidence to suggest that similar principles apply to adult patients and that operative correction using MIRPE can be achieved in this population. ^{[20, 21]}

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 anatomic deformity. ^[22]

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. ^[23] The results were good to excellent in the majority of adults, and there were no major complications or further recurrences. Another study found that a modified MIRPE could be successfully used in most adults to revise a failed prior Nuss procedure. ^[24]

Patients with other associated complex congenital anomalies, neurodevelopmental delay, congenital heart disease with primary cardiac dysfunction, and chronic immunosuppression are not considered good candidates for corrective surgery for pectus excavatum. A comprehensive preoperative evaluation, including cardiology consultation and echocardiography, must be completed in order to determine the patient’s level of risk.

Best practices

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.

Procedural planning

Patients must be selected carefully for the procedure. Preoperative assessment may include pulmonary function testing (PFT) and noncontrast CT of the chest. CT allows determination of the preoperative Haller index (as previously described). Patients with a Haller index higher than 3.2 are considered candidates for MIRPE. PFT typically demonstrates mild changes in pulmonary volumes (restrictive pattern). ^[25] Echocardiography is performed selectively in patients with clinical evidence of Marfan syndrome or with any cardiac symptoms or murmurs.

Complication prevention

Appropriate patient selection and careful attention to operative and technical details minimize the risk of complications. ^[26] Moreover, recognizing that the ideal age for operative repair is between 8 and 12 years of age is important. ^[27] 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. ^[18]

Several studies have been published that evaluate the short and long-term outcomes after MIRPE. Overall patient and family satisfaction has been considered very good, with excellent and good results reported in more than 90% of cases. ^{[28, 29, 26]}

In 2000, a multi-institutional study that reviewed 251 MIRPE cases demonstrated a significant complication rate (overall incidence of complications was almost 20%). ^[26] 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. ^{[28, 26]} This probably reflects the learning curve associated with the introduction of MIRPE. Since the first such procedure was performed, the bar has been modified several times; current bars are strong enough to withstand the pressure of even the most severe deformity.

Factors contributing to the suboptimal results reported include the softness of the bars initially used, the premature removal of the bar, and the failure to stabilize the bar adequately. ^[30] 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. ^[31]

The spectrum of adverse outcomes is variable, and most complications are considered rare and unusual. ^{[28, 26, 32, 33, 34, 27]} The following is a list of reported complications after MIRPE (and their estimated incidence):

• Pectus bar displacement ^[35] 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, one study 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. ^[25]

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 not 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. ^[36]  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. ^[37] 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%. ^[18]

A 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 MIRPE. ^[38]  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 (FVC) 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. ^[8]  Once the cartilage and bony structures are remodeled, normal or improved pulmonary function is established and the flexibility and malleability of the chest remains 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 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. ^[39]

Final data analysis generated by the multicenter study and published in 2013 clearly demonstrated that there is significant improvement in lung function at rest and in VO₂ max and O₂ pulse oximetry after surgical correction of pectus excavatum with a Haller index greater than 3.2. The study concluded that operative correction significantly reduces the Haller index and markedly improves the shape of the entire chest and cardiopulmonary function. ^[40]

The Nuss procedure has been associated with a greater degree of postoperative pain than the Ravitch procedure. However, a meta-analysis of 19 studies (N = 1731) found that the postoperative length of stay was similar for the two procedures and that the Nuss procedure (n = 989) was associated with shorter operating times and less blood loss than the Ravitch procedure (n = 742). ^[41]

Toci et al assessed outcomes in 290 adults undergoing Ravitch (n = 53) or Nuss procedures (n = 237) for pectus excavatum to determine whether postoperative complications and recurrence differed significantly between primary and redo operations. ^[42]  There were no significant differences in postoperative complications or recurrence rates between Nuss and Ravitch repairs overall, between redo Nuss repairs (n = 53) and Ravitch repairs (n = 26), between primary and redo Nuss repairs, or between primary and redo Ravitch repairs; however, there were significant differences between all Nuss and all Ravitch repairs with respect to age, length of stay, follow-up, bars inserted, and estimated blood loss.

It is important to note that there is a risk of significant complications with both the open and the minimally invasive approach to repair of pectus excavatum. A 2018 study reported the types of life-threatening complications related to minimally invasive repair. ^[43] As expected, the overall incidence of such complications was quite low (< 0.1%) and was not dissimilar to that associated with the open repair. Surgeons performing minimally invasive repairs must familiarize themselves with the potential complications in order to minimize the risk of unfavorable outcomes.

In a retrospective study using data from the American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP), Brungardt et al compared the outcomes of minimally invasive (Nuss) and open (Ravitch) repair in 168 patients aged 18 years or older with pectus excavatum as the postoperative diagnosis. ^[44] Median operating time was 250 minutes in the Ravitch group and 122 minutes in the Nuss group; median LOS was 5 days in the Ravitch group and 3 days in the Nuss group. Postoperative complication rates were similar in the two groups.