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Ann Thorac Surg 2004;77:289-295
© 2004 The Society of Thoracic Surgeons
a Department of Thoracic and Cardiovascular Surgery, Soonchunhyang University, Chunan Hospital, Chunan, South Korea
* Address reprint requests to Dr Park, Department of Thoracic and Cardiovascular Surgery, Soonchunhyang University, Chunan Hospital, 23-20 Bongmyung-Dong, Chunan 330-100, South Korea.
e-mail: hyjpark{at}sch.ac.kr
Presented at the Thirty-ninth Annual Meeting of The Society of Thoracic Surgeons, San Diego, CA, Jan 31–Feb 2, 2003.
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Abstract |
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 Top Abstract IntroductionPatients and methodsResultsCommentAcknowledgmentsDiscussionReferences |
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METHODS: We retrospectively reviewed 322 consecutive patients who underwent repair of pectus excavatum by the Nuss technique and its modifications between August 1999 and June 2002. Of the patients 251 (78%) were children and 71 (22%) were adults. Precise morphologic characterization of the pectus allowed appropriate shaping of the bar to achieve a symmetric repair.
RESULTS: Of the 322, 185 (57%) had symmetric and 137 (43%) had asymmetric pectus excavatum. Within the asymmetric group 71 were eccentric, 47 were unbalanced, and 19 were combined. Modifications to the shape of the bar including asymmetric and seagull bars were developed to deal with these types of asymmetry. A double bar or compound bar technique was used in most of the adults. Multipoint wire fixations to ribs were utilized to prevent bar rotation. Postoperative complications included pneumothorax (n = 24, 7.5%) and bar displacement (n = 11, 3.4%). The bar was removed in 42 patients 2 years after the initial procedure.
CONCLUSIONS: Precise morphologic classification has led to modifications of the Nuss technique that facilitate correction of virtually all varieties of pectus excavatum including patients with asymmetric varieties and adults.
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Introduction |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsDiscussionReferences |
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Patients and methods |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsDiscussionReferences |
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Morphologic classification of the pectus excavatum
Given the wide spectrum of morphologic variations of the pectus excavatum, we believe it is necessary to employ techniques tailored to each variant for optimal results. One of the authors (H.J.P.) created a morphologic classification system to facilitate decision making.
Figure 1 is a series of computed tomography (CT) scans that illustrate the various subtypes we have identified. The classification begins by sorting the deformities into symmetric ("type 1") and asymmetric ("type 2") varieties. In the symmetric types (1A and 1B in Fig 1), the center of the sternum (C point) and the center of the depression (P point) are colocated. Type 1A is the typical deep symmetrical depression of the lower sternum. Type 1B is the broad, flat type, rather than a deep focal depression.
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< ß). Types 2A and 2B can be further subdivided into focal type (2A1, 2B1) and broad-flat type (2A2, 2B2). One of the most extreme forms of eccentric varieties is the long canal type ("Grand Canyon" type, 2A3), which is a deep longitudinal groove from the clavicle all the way down to the lower chest. In the Grand Canyon type most of the depression is in the parasternal cartilage not the sternum. Type 2C is a combination of types 2A and 2B.
The CT Index (CTI [transverse diameter/vertical diameter]) [7] was also determined for each patient from the CT scan.
Operative procedure
The concept of the technique is that a retrosternal metal bar supported at bilateral hinge-points raises the depressed chest wall. Each hinge-point (H point) is an intercostal space located at the crest of the depression on either side and is the point where the bar penetrates the pleural cavity.
C, P, and H points of the deformity are determined and marked on the patient's chest wall. Then small incisions are made bilaterally at the midaxillary line and subcutaneous tunnels to the hinge-points are created. The hinge-point is penetrated with a right angle clamp and then a pectus clamp is passed through at this point into the pleural cavity. The pectus clamp is advanced carefully across the mediastinum under the depressed sternum and emerges through the hinge-point on the other side and finally through the corresponding skin incision. A guide (currently, 32F chest tube) is grasped by the clamp and pulled through the pathway that has been created. This guide is then used to pull through a metal bar (Walter Lorenz Surgical, Jacksonville, FL), which has an appropriate shape for the morphologic type of the deformity (see below). The bar is passed with the convexity facing dorsally, along the curvature of the depressed sternum. Once in place the bar is then rotated 180 degrees around the axis of the hinge points, thus elevating the depression. Both ends of the bar and one hinge-point are then fixed to the ribs by the method described below and the skin incisions closed.
Technical modifications: bar shaping
An appropriate sized bar is selected. Bar size is determined by the length between bilateral midaxillary lines, and the points corresponding to the C and P points are marked on the bar. The bar is then shaped at the operating table to account for the morphologic type of pectus as depicted in Figure 2.
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For type 2 (asymmetric) pectus we create an asymmetric bar based on the morphology of the pectus. For type 2A pectus we shape a bar that places the maximum convexity of the bar corresponding to point P, the deepest point of the pectus depression (Fig 2.3). For type 2B, the unbalanced pectus, or type 2C, the combined type, a seagull shaped bar was made by creating a notch in the bar corresponding the point of chest protrusion (E point; Fig 2.4).
For adult patients we made additional modifications. To facilitate more central elevation, a "hump-shaped bar" was designed to include a segment of exaggerated central convexity (Fig 2.5). This design provides more resistance to pressure. The stiffness can be further enhanced as necessary to a "compound bar" by placing a smaller central arc between each hinge-point and adjoining at either side by two larger arcs (D > D'; Fig 2.6).
Other modifications
To place the retrosternal bar exactly at the bottom of the depression, the bar can be placed obliquely using different levels of hinge-points in order to achieve better correction. In cases of the broad or long depressions, two bars are inserted at superior and inferior levels parallel to each other (parallel bar technique).
For larger adults a double bar can be made by affixing a 2-inch smaller supplementary bar to inside of the main bar.
Bar fixation: the Five-Point fixation
Fixation of the bar to prevent rotation or displacement is important. Our current technique fixes the bar at five points (Fig 3).
At both ends of the bar (Fig 3, A) steel wires encircle the rib above and the rib below, each wire is passing through the end-hole of the bar. A fifth wire is added on the right side at the hinge-point, which encircles the bar and a rib together (Fig 3, B). The pericostal wire sutures are not placed through the lateral incisions rather by piercing the skin over the ribs as it was not possible to place sutures through the incisions. Once placed percutaneously the ends of the pericostal wires can be easily accessed by subcutaneous dissection through the skin incision and knotted to the bar. This maneuver made it possible to do all necessary pericostal sutures through the single tiny incision on each side, even in the parallel bar technique where there are as many as seven or eight pericostal wires.
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Results |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsDiscussionReferences |
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Distribution of procedures
Table 2
lists the distribution of the various techniques we have utilized throughout the series as a whole. Over time some techniques have replaced others. It should be noted that the compound bar was only recently introduced in February 2002, which replaced the double bar. Central fixation (Fig 2, 5) was employed for 10 patients who had reoperation for failed previous Ravitch or sternal turnover procedure.
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Complications and hospital stay
Table 3
lists 61 complications for an overall complication rate of 18.9%. Of these, 15.2% were early complications (<30 days postoperative) and 3.7% were late. We classify 4.0% of these complications as major including major bar displacement (4), pericarditis (8), and premature bar removal (1).
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Pericarditis and pericardial effusions have emerged as serious complications in our series. We recommend immediate echocardiography for any febrile patient to facilitate early diagnosis. Conservative management or percutaneous catheter drainage has resolved the acute effusion in all instances but 1 patient developed chronic constrictive pericarditis.
Injury to the heart or other mediastinal structures is rare yet the most tragic complication of the procedure. We had one case of cardiac perforation during the procedure. This was a reoperation for displaced bar, which had been inserted in another hospital 1 year prior. There were likely adhesions in the thorax and the pectus clamp penetrated the right atrium and the right ventricle. The cardiac injury was repaired successfully.
The other complications (14.9%) were minor and self-limited. The most common minor complication was pneumothorax. These were most common in adults or asymmetrical pectus repairs, which were more extensive procedures. In these cases we now electively insert Hemo-Vac catheters (Sewoon Medical Co, Ltd, Hwasung, Kyunggi, South Korea) into the pleural space.
We noted no adverse effect of the Nuss bar outside of those listed complications. Specifically we did not observe somatic outgrowth during the 2 years they were in place. Median hospital stay was 5 days (range, 3 to 22) for children and 7 days (range, 4 to 16) for adults.
Bar removal
Forty-four patients (13.7%) have had the bar removed; 42 were electively removed as a completion procedure 2 years after the initial operation. However the other two were removed prematurely at 1 year: one because of persisting wound infection and the other at the patient's request. In all 42 patients who have had the bar removed, contour of the initial correction was maintained.
Reoperation
Fourteen patients (4.3%) underwent reoperation. The most common cause was the bar displacement as listed in Table 3. Two other patients had reoperation due to a progressive deterioration of the contour. One of them had Marfan syndrome. One patient was reoperated on for a skin perforation by the stabilizer.
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Comment |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsDiscussionReferences |
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The central concept of our technique is the recognition of the point to be elevated. That point is the deepest part of the depression (P point). It is this area, not necessarily the center of the sternum (C point), that should be elevated. Selection of hinge-points is another point of importance and we have liberally used oblique positioning when this seemed indicated.
Previous authors have reported difficulty in dealing with asymmetry [8]. In this setting the standard symmetrical bar cannot elevate the depression to the target level without excessive protrusion of the other side. Hence we have tailored asymmetric bars to correct asymmetric types of pectus, causing maximal elevation pressure on the most depressed point in the deformity, wherever it is located.
One of the most challenging morphologies is the unbalanced type of asymmetrical pectus (type 2B). In this setting (Fig 1, insert 2B) a portion of the chest (the E point) is already elevated. The important part of the technique for this variety is to inhibit the further elevation of this area. The function of the seagull shaped bar in combination with the crest compression technique is that the protruded rib (E point) becomes the hinge-point on that side, which tends to depress that point instead of elevating it. In cases of broad or long depression such as the Grand Canyon type, the parallel bar technique was applied.
Use of the Nuss procedure in adults is a relatively new development [15]. The problem has been that the conventional single bar failed to elevate the heavy chest due to loss of the arc and consequently both tips of the bar separated from the lateral chest wall at the hinge points. We developed the double bar technique to overcome this problem and we were initially pleased with the results in our first 20 adults. Subsequently we have developed the compound bar technique and find this modification even more effective. The compound bar is an incorporation of exaggerated convexity in the center of the bar. The concept is a circle with a smaller diameter bearing a heavier load. The compound bar simultaneously resolved the most difficult issues, namely the smaller central arc makes the bar convex enough to elevate the depression and the larger lateral arcs can adjust the width of the bar easily to fit the size of the chest.
There has been a substantial rate of bar displacement with Nuss' original fixation technique [8–10, 12, 16–18]. This occurs more frequently in the severely asymmetric pectus or adult patients. We have observed a variety of mechanisms of bar displacements. Patterns of bar displacement are flipping, lateral sliding, and backward shift (hinge-point breaking). Flipping, the most common, is a rotation of the bar as it pivots on the hinge-point. Lateral sliding of the bar occurs in cases of severe eccentric asymmetry because uneven pressure on each side makes the bar slide down toward the depressed side. Backward shift of the bar occurs when intercostal attachment breaks down because of excessive pressure of the adult chest or uneven pressure of severe asymmetry. Consequently the bar fails to lift the depression to the target level because of posterior movement of the hinge-points.
To prevent the bar displacement, strategies for the fixation should be individualized by anticipating the most likely mechanism of displacement. For the symmetric type we have found the standard five-point fixation is sufficient. For the eccentric types additional support at the depressed side with a stabilizer is necessary in order to block the lateral sliding of the bar. In cases of hinge-point disruption wire reinforcement of the hinge rib should be employed. Other authors have proposed different techniques for the bar fixation [8, 19, 20]; however we have found that our techniques based on morphology seem to be more efficient than others in terms of stability, simplicity, and the ultimate scar. Bar displacement rates in the literature were variable but relatively high. It was 9.2% in a multiinstitutional survey in the United States [8] and other centers showed the rates varying from 4.2% to 19% [9, 10, 12, 18]. Our rates of bar displacement (3.4% overall and 1.2% major displacement) compare quite favorably. While our total complication rate of 18.9% may seem high, most of the complications were self-limited.
Pectus bar removal as a completion procedure is performed after 2 years of bar insertion. The bar removal procedure has generally been uneventful except for frequent wound seromas. One patient required a premature bar removal 1 year after the procedure because of persistent wound infection. Six months after bar removal there has been no change of chest configuration.
We conclude that understanding of the precise morphologic characteristics of pectus excavatum has allowed us to refine and develop techniques to deal with all types of the deformity. That has allowed us to expand the indications of the Nuss procedure to asymmetric types and adult patients.
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Acknowledgments |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsDiscussionReferences |
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Discussion |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsDiscussionReferences |
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The Nuss technique is generally described as a minimally invasive technique for repair of pectus excavatum. It is true that it is much less invasive than the classic Ravitch repair; however it is different than most minimally invasive techniques. With most minimally invasive techniques, essentially the same operation is done as in the standard technique. It is simply done through smaller incisions or through ports using scopes and special instrumentations. In the Nuss repair however the goal of correcting the chest wall deformity is accomplished by an entirely different method than that used in the standard technique. Instead of resecting the costal cartilages and doing a sternal osteotomy, the chest wall is remodeled by pressure from the metal bar. If the correction with this technique proves to be durable, the long-term results should be better than the result after the standard open repair. That is because the costal cartilages remain intact and therefore the chest wall should maintain its normal strength and flexibility. In addition the new techniques described today may improve or correct the disparity in the radius of curvature of the ribs on the right and left sides that is seen in the asymmetric types. This aspect of the deformity is not addressed at all with the standard Ravitch repair. To date much emphasis has been put on the minimally invasive aspect of the Nuss technique. A superior long-term result with this technique may eventually prove to be much more important.
The authors are the first to report a large series using modifications of the Nuss technique to extend its applicability. In addition to these creative modifications they have also given us a system for classification that will be important in future reporting.
Finally this is a very promising but nevertheless new technique with a new set of risks and potential complications. We need to apply it cautiously until the long-term results are known, particularly for adults in whom the chest wall is less compliant.
I have only two questions for Dr Park. First, in the patients who had their bar removed, have you found that the adults maintain their correction as well as the pediatric group? Second, your technique of bar fixation with circumferential wires around the ribs is simple and effective. Has it resulted in any symptoms suggesting intercostal nerve entrapment?
I thank Dr Park for allowing me to review his manuscript before the meeting and I congratulate him on this fine work. I also thank the Society for the privilege of discussing this paper.
DR LEIF C. DERNEVIK (Gothenburg, Sweden): I wonder if the correction has only a cosmetic effect or if you can detect some improvement in pulmonary and cardiac function afterwards? And if the purpose is only cosmetic, wouldn't it be more simple to just put a silicone prosthesis under the skin?
DR PARK: Thank you, Dr Palmer, for your kind comments and questions. You have pointed out an important issue regarding results in the adult population. To date there are no published data for adult patients so we simply don't know what is the adequate length of time to maintain the bar in for long-term results. Actually I have not removed the bars from the patients older than 20 years yet so I can only suggest my consideration but I am a bit on the optimistic side.
I have had a few patients who have undergone bar removal earlier than planned because of their persistent wound problems. What I have found was a good maintenance of the correction for up to 1 year of follow-up, even though the bars were removed only 1 year after their initial operation. So now I am considering whether we can remove the bar 2 to 3 years after the operation in selective cases but it remains to be seen.
In response to your second question regarding the neural damage, I agree with you that intercostal nerve damage must be a concern related to the fixation technique. The risk of nerve damage is minimal however. My technique involves muscle tissue rather than simply encircling the ribs. I am happy to report absolutely no incidence of intercostal nerve damage so far.
As for the third question regarding pulmonary or cardiac function improvements and some other cosmetic methods, actually I did not compare my results with other techniques but I believe that this technique is much more physiologic repair than the other method. Particularly just putting some braces or something beneath the skin would not be a good method. I have observed that many patients had a rapid growth after the operation and relief of symptoms like shortness of breath and frequent upper respiratory infections. That would be promising for a further study.
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References |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsDiscussionReferences |
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