Modified bar bending method of thoracoscopic nuss procedure on pectus excavatum: a retrospective single-center study

Pectus excavatum (PE) is a congenital abnormality, which is characterized by the backward bending of the ribs in the middle and lower sternum and the two sides, causing the anterior chest wall to recess backward into a funnel, with the sex ratio tends to be close to 4–6:1 (male: female) and the incidence rate as high as 2–3/1000 [1, 2]. Additionally, familial inheritance has been recorded, with a familial occurrence rate of 54% [3]. Secondary cardiopulmonary dysfunction, chest pain, dyspnoea, and exercise intolerance can be caused by PE [4‐7]. Besides, the psychological impact of shame, depression, and distress are well known [7].

Surgical correction remains the definitive management of PE, and many procedures have been applied to correct this malformation. Traditionally, the Ravitch procedure is performed, in which the abnormal cartilage is resected, and the sternum is fractured and fixed in a corrected position [7‐9]. In 1998, the "Nuss procedure" was proposed by Donald Nuss, with the feature of minimal trauma and blood loss, shorter operating time with good postoperative results and satisfaction, and a low rate of complications [10, 11]. Nowadays, the Nuss procedure has become the standard operation for pectus excavatum repair, but it also has some disadvantages.

The bar of the traditional Nuss procedure is bent into an arc generally, and the crest of the arc is used to support the lowest point of the sternum for orthopedics [12]. But this bending method has poor support stability and is prone to bar migration and rotation according to our clinical experience. We present a novel modification to the bending method of Nuss procedure which is the modified bar bending method of the six-point seven-section type.

This study aimed to analyze the efficiency of the intraoperative and postoperative outcomes of the novel modification of the Nuss corrective procedure for the treatment of pectus excavatum in young adolescents at our hospital.

Methods

Forty-six cases of PE children treated with the modified bar bending method of the six-point seven-section type were selected as group A from January 2019 to December 2021. 29 cases (63%) were divided into type I (symmetric) and 17 cases (37%) were divided into type II (asymmetric) according to Park's classification [14]. 35 cases (76%) were male and 11 cases (24%) were female. The median age was 12 (IQR 5, 13). The median Haller index was 5.63 (IQR 4.08, 7.72). 28 (60.9%) patients were with shortness of breath after exercise.

Fifty-one children with PE treated by the traditional curved bar bending method between January 2016 and December 2018 were selected as Group B, and the case data of this group were summarized above. type I (symmetric) in 34 cases (66.7%), type II (asymmetric) in 17 cases (33.3%), male patients in 40 cases (78.4%), and female in 11 cases (21.6%) among the patients. The median age was 12 (IQR 6, 15). The median Haller index is 5.87 (IQR 4.15, 7.95). 32 (60.9%) patients were with shortness of breath after exercise.

There was no difference in Park type (P = 0.71), sex (P = 0.78), age (P = 0.58), Haller index (P = 0.27), or shortness of breath after exercise (P = 0.85). The demographic data of the patients are shown in Table 1.

No statistical difference existed among all indicators, no other associated malformation happened, and no serious cardiopulmonary dysfunction or respiratory tract infection symptoms existed before surgery. Surgery for groups was performed by the same treatment group and a bar was inserted above the two groups. Both groups were operated on without massive bleeding successfully. The intraoperative, postoperative, and follow-up data were summarized and analyzed as follows.

The median (IQR) procedure duration was significantly decreased in group A than Group B( 90 (IQR 70, 110) VS 90 (IQR 70, 110), p = 0.008), which is due to the decrease in bar bending time (14 (IQR 10, 16) VS 23 (IQR 20, 27), P < 0.001). Besides, there was no difference in operation time (74 (IQR 65, 82) VS 75 (IQR 70,85), P = 0.13) and intraoperative blood loss (6 (IQR 3, 8) VS 6 (IQR 4, 8), P = 0.23) between the two groups. The Comparison of intraoperative data is shown in Table 2.

The postoperative CRP elevation time (4 (IQR 3,6) VS 5 (IQR 4,6), P = 0.72), the duration of postoperative fever time (3.1 ± 1.1 VS 3.6 ± 1.5, P > 0.05), and the duration of antibiotic use (7.3 ± 2.1 VS7.4 ± 2.8, P > 0.05) were similar between the two groups without statistical difference. However, the duration of postoperative pain in group A was shorter than that in group B (3.1 ± 1.2 VS 7.5 ± 1.3, P < 0.05). The list of Outcomes after treatment is shown in Table 3.

The evaluation criteria for postoperative effects are as follows:

If it meets 4 criteria, it is preferable; 3 are good; 2 are medium; 0 to 1 is poor. As a result, there was no "poor" case in the A and B groups, and there was no statistical difference in the proportion of "excellent", "good" and "medium" cases according to the above evaluation criteria (Fig. 3) (Fig. 4).

Early complications were recorded in 19 patients (19.6%), and late complications were reported in 4 (4.1%), while intraoperative complications were not recorded. The most common early complications were closed pneumothorax, followed by pneumonia and pleurisy and poor healing of incision, while two patients had pleural effusion. The most common late complication was bar migration.

For common complications, there was no difference in closed pneumothorax (3 (6.5%) VS 4 (7.8%), P = 1.00), pleural effusion (1 (2.2%) VS 1 (2.0%), P = 1.00), pneumonia and pleurisy (2 (4.3%),4.3% VS 3 (5.9%), P = 1.00) and the incidence of poor incision healing (2 (4.3%) VS 3 (5.9%), P = 1.00) between two groups. As for bar migration, no case happened in group A and 4 (7.8%) cases happened in group B, and there was no difference between the two groups (P = 1.00). The list of complications by patient is shown in Table 4.

The patients with closed pneumothorax and pleural effusions were treated conservatively (antibiotic and corticosteroid therapy) without the need for thoracal drainage and resolved within two weeks. Five cases of pneumonia and pleurisy were treated conservatively with antibiotics. Additionally, all four late bar migrations were less than 40 degrees of rotatory migration (rotational bar movement-torsion) and did not need surgical reintervention. Surgical complications according to Clavien–Dindo classification are shown in Table 5.

Pectus excavatum (PE) is the most common disease of chest wall deformity. Although the Nuss procedure has been widely carried out around the world some improvements based on the traditional Nuss procedure can still bring benefits to patients [15]. This study proved that compared with the traditional Nuss procedure, the modified bar bending method of the thoracoscopic Nuss procedure was reduced significantly in the procedure duration, bar bending time, and duration of postoperative time. And there was no difference in the evaluation of postoperative effects, bar migration, postoperative complications, Clavien- Dindo classification of surgical complications, operative safety, and operative validity, compared with traditional Nuss procedure.

Since the introduction of the Nuss procedure, many modifications have been proposed to improve outcomes and safety. But the improvement regarding the bending step was adequate. In our study, several cases of postoperative complications of bar migration happened in traditional Nuss procedure, which prompted us to analyze the phenomenon. The traditional bar is bent into an arc shape, which overemphasizes sternum elevation in the central position [12]. And owing to the power of the sternum elevation being concentrated, the duration of postoperative pain is longer. Besides, the circular shape is required to bend the whole bar severally with bending equipment to adapt to the chest shape, which takes a long time and does more harm to the patients. For children before adolescence, bar shifting incidence is lower on account of the hardness of the sternum and ribs is lower slightly. And the probability of bar migration increased significantly for adolescents alone with the bone growth solidified and muscles getting strong [16]. Thus, the design of the bar could sustain the hard sternum is important affairs. Given the above defects, we improved the design of the modified bar bending method, which is the six-point seven-section type. The advantages of this modified method are as follows:

Consulting literature, a series of modifications focused on the parts of measuring the chest, bar selection and configuration, marking the patient, thoracoscopy, subcutaneous tunneling, substernal tunneling, sternal elevation, bar insertion and rotation, bar fixation, pneumothorax evacuation [17]. Anthony I. Squillaro et al. [18] emphasized the importance of chest introducer entry and exit sites as a critical operative step, which is a novel alternative approach to asymmetric pectus excavatum repair. Guoqing Li [19, 20] introduced the modified Nuss procedure operating with right unilateral thoracoscopy and a new bar of fixed bend, which overcomes the necessity of bar turning over with the advantages of less invasive and more safety. The median of total operating time in this article is 70 min, which is shorter than our modified procedure. And the difference also confirm that the time of bending bar cost much time. A. Durry, W. Rainey Johnson, R. Kabbaj et al. [21‐23] added a subxiphoid incision to improve the visualization of the anterior mediastinum and limit the risk of cardiac or pericardial perforation. But the duration of operation gets longer which could generate complications. There is no difference between the Thoracoscopic extrapleural modification of the Nuss procedure and the standard Nuss procedure [24]. KristaLai et al. [25] described cryoablation as an effective method of postoperative analgesia, and the expectation is that patients will be off opioid analgesics by 1-week postoperatively. And applying cryoablation could decrease the length of stay, control pain, and result in overall cost savings.

While this study proposes a novel alternative bending approach to pectus excavatum repair, the nature of a technical report from a single center and single surgeon experience are key limitations to this technical report. Several items like the incidence of bar migration in our patients and how they relate to the success of our modified method have yet to be analytically examined. A multiple-center prospective study with a large number of cases will be needed to further draw our conclusion.

In conclusion, the modified bar bending method confirms fixed points to bend the bar, which reduces the operation time and duration of postoperative pain, while the safety, the incidence of postoperative bar migration, effectiveness, and satisfactory effect remain the same. Apart from this, the modified method shows the characteristics of a minimally invasive Nuss procedure. Thus, the modified surgical method is worthy of popularization and application.