Nuss Procedure for Pectus Excavatum
- Author: Andre Hebra, MD; Chief Editor: Dale K Mueller, MD more...
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. The image below illustrates the typical appearance of a teenaged boy with a severe pectus excavatum (A) and a young girl (B) with the pectus deformity.
Pectus excavatum occurs in an estimated 1 in 300-500 births, with a male predominance (male-to-female ratio of 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.
This topic focuses on the operative technique known as the minimally invasive repair of pectus excavatum (MIRPE). It was originally described by Dr. Nuss and, for that reason, it 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. Not until May of 1997 was this new and innovative technique introduced to the American Pediatric Surgical Association and, subsequently, published in the Journal of Pediatric Surgery. Because of the early excellent results obtained with this new technique and because of the less radical nature of the operation (compared to the open Ravitch technique),[4, 5, 6, 7] the popularity of this approach has grown dramatically. The image below illustrates the before and after appearance of the chest of a 14-year-old patient treated for pectus excavatum using the minimally invasive technique.
Pectus excavatum patients are considered candidates for corrective surgery based on the following criteria:
The severity of the deformity (the severity is determined by the measurement of the chest Haller index)
The resulting functional impairment
The psychosocial impact of the deformity on the patient
The chest Haller index is a measurement taken from a noncontrast 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 (see the first 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. Even if asymptomatic, those patients usually benefit from the corrective surgery.
Of note, obtaining a chest Haller index in a young patient (see second image below) with pectus excavatum is not necessary. The Haller index should be obtained prior to the time of corrective surgery (within months and not years) such that it can provide information helpful to the surgeon in planning the operative correction of the pectus.[10, 11]
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 tests and an echocardiogram 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. However, upon further questioning, 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 don't want 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 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 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 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, one should not view operative correction of pectus excavatum as an operation limited exclusively to pediatric patients. Indeed, the open technique has been used in adult patients with excellent results. However, experience with the MIRPE in adult patients has been limited to a few cases, reported in anecdotes.
Early results seem to indicate that similar principles apply and that operative correction using MIRPE can be achieved in adult patients. Limiting factors 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.
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. Comprehensive preoperative evaluation, including cardiology consultation and echocardiogram, must be completed in order to determine the patient’s risk assessment.
Not all patients with pectus excavatum are considered candidates for corrective surgery. The decision to undergo surgery is based on clinical symptoms and severity of the deformity. The surgeon, patient, and immediate family must reach a consensus as to the benefits of operative repair of 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 CT scan of the chest without contrast. The CT scan allows for 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. The PFT typically demonstrates mild changes in pulmonary volumes (restrictive pattern). Echocardiography is performed selectively in patients with clinical evidence of Marfan syndrome and/or with any cardiac symptoms or murmurs.
Appropriate patient selection and 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 when compared to teenagers and young adults.
Several studies have been published that evaluate the short and long-term outcomes of patients following minimally invasive repair of pectus excavatum. The overall patient and family satisfaction has been considered very good, with excellent and good results reported in more than 90% of cases.[24, 25, 22]
In 2000, 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%). The most common complication requiring 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 more rigid chest cage.
Review of the literature has demonstrated that a relatively high rate of complications was reported when many different surgeons performed the operation.[24, 22] This probably reflects 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. Factors contributing to the suboptimal results reported include the fact that 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) can minimize the occurrence of bar displacement.
The spectrum of adverse outcomes is variable, and most complications are considered rare and unusual.[24, 22, 28, 29, 30, 23] The following is a list of reported complications after MIRPE (and the estimated incidence):
Pectus bar displacement requiring reoperation (2.5%)
Pneumothorax requiring chest tube (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%)
In relationship to cardiopulmonary outcomes after MIRPE, a study has demonstrated that objective measures of FEV1, total lung capacity, diffusing lung capacity, and respiratory quotient all showed significant improvement (after bar removal) compared to preoperative values, while normalized values of cardiac index at rest did not. Note 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 minimally invasive technique.
Some surgeons have discussed what technique (MIRPE vs open surgery) provides the best 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, no prospective randomized published data is available to support this approach.
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 forced expiratory volume in one second is typically decreased by more than 50% of predicted reference range levels.
With the 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 remains unaffected.
Critics of the MIRPE claim that the Nuss procedure is too invasive, risky, and not pain free. Proponents argue that this new approach, compared with the 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. The MIRPE allows for a much shorter operating time, minimal blood loss, and minimal surgical chest wall scar. Moreover, the stability and strength of the chest wall is not compromised as it can be with the open repair.
Data published in 2011 by the multi-center study group evaluating the pulmonary functional outcome of pediatric patients with pectus excavatum treated with MIRPE has 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 multi-center study and published in 2013 clearly demonstrated that there is significant improvement in lung function at rest and in VO2 max and O2 pulse oxymetry after surgical correction of pectus excavatum, with CT index >3.2. The study concluded that operative correction significantly reduces CT index and markedly improves the shape of the entire chest and cardio-pulmonary function.
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