Lung, Chest Cavity, and Dorsal Spine Surgery

Abstract

The thorax is a dynamic system that enables normal breathing. Malformation of any component (vertebrae, sternum, ribs or muscles) may impair respiratory function and could require surgery for repair. The most frequent thorax malformations are pectus excavatum and pectus carinatum. The most frequent acquired condition is kyphoscoliosis. Surgery may improve lung function and quality of life in many patients.

Introduction

The subtle interaction between the chest and its contents is not only evidenced in the pathological states where restrictive ventilatory complications determine alterations in the chest. In particular, the critical periods of the developments of pathologies that affect the chest cavity or its components (e.g., dorsal spine or sternum) can provoke changes not only in ventilatory mechanics but also disturbances in the concomitant development of the lung parenchyma (e.g., alveolar multiplication) that could eventually cause permanent functional cardiopulmonary sequelae. In this chapter we address the eventual functional effects of the pathologies and the treatments that directly affect the chest or its components.

Surgery of Congenital Malformations of the Chest Cavity

The thorax is composed by multiple independent bones (vertebrae, sternum, and ribs) that form the chest cavity along with several muscles that cover it. The chest cavity is often seen only as protection for intrathoracic organs, but the chest is a dynamic system that enables respiratory function. Thus, any condition that results in its malfunction will significantly affect the respiratory system and the intrathoracic organs.

Malformation of the chest cavity means any abnormality that affects the normal structure and impairs chest function. These malformations can be divided into two main categories: congenital and acquired. The deformities of the chest cavity can be divided into two groups: the ones that have a depression or protrusion of the sternum and those that have different degrees of aplasia or dysplasia (Table 72.1). The most frequent malformations are pectus excavatum (88%) and pectus carinatum (5%), which we will describe in this chapter.

Table 72.1 Congenital malformations of the chest cavity

Pectus Excavatum

Pectus excavatum is the anterior depression of the costal wall. It is the most common malformation of the chest cavity, with an incidence of 1 in 400 births. It is more common in men than in women, with a ratio of 5:1. It is more common in the white race, and it is more frequently presented from the first year of life, progressing and becoming more noticeable during the puberty growing phase. The mechanism that provokes it is not completely identified. Some histological studies have shown a weakening in the components of the costal cartilages, which would allow for posterior sternal migration. There is no chromosomal defect, but it has been reported in conjunction with Marfan syndrome, Ehlers–Danlos syndrome, osteogenesis imperfecta, syndactyly, and Klippel–Feil syndrome. Also, a genetic predisposition of approximately 40% of the patients has been detected, who report having a family member with medical history of being a carrier of a malformation of the chest wall.

Preoperative Evaluation

The objective of the preoperative evaluation is to define the morphology and seriousness of the deformation of the sternum, and its functional repercussions both in the lungs and the heart. It is also important to demonstrate that the subject is not allergic to the metallic compounds used when repairing the pectus excavatum, which is present in 2% of the cases.

Computerized tomography or magnetic resonance is used in the evaluation of the level of seriousness of the pectus excavatum when calculating the Haller index. This consists in the transverse diameter of the chest divided by the anteroposterior diameter of the point of the sternum with the greatest depression (Fig. 72.1).

Fig. 72.1

Haller index (TAC)

In the lung evaluation, abnormalities in the lung function can be shown by measuring the forced vital capacity, forced expiratory volume in 1 second, and forced expiratory flow of 25–75% of the forced vital capacity.

Regarding the cardiac assessment, the echocardiographic assessment is important, which can show cardiac compression with alterations in the filling and emptying of the right ventricle, while showing deformations of the mitral ring, with prolapse and regurgitation of the mitral valve.

The symptoms produced in the patient are an important part of the preoperative evaluation. Symptoms, such as exercise intolerance, low endurance, and shortness of breath, are reported by the patients with pectus excavatum. Another important aspect is the cosmetic effect that this produces. It limits the normal life of some patients, because they avoid places where the chest deformity will have to be exposed, such as the beach or pools. It has been proven that patients with pectus excavatum have a lower quality of life and that the treatment statistically improves their bodily image.

Treatment

Surgical correction for pectus excavatum is recommended when the patient has one of the following criteria:

• 1. Computerized axial tomography or magnetic resonance that shows heart or lung compression with a Haller index of 3.25 or more.

• 2. Restrictive lung disease proven by a lung function test.

• 3. Heart compression with abnormalities in the mitral valve, either prolapse or regurgitation.

• 4. Exercise intolerance, decrease in endurance, and shortness of breath during exercise.

• 5. Recurrence after an open or minimally invasive surgery.

• 6. Cosmetic effect produced in patients.

The optimal correction age is between 10 and 14 years of age. In this period the chest cavity is more malleable, which allows for a lower rate of recurrence.

Today, the surgical treatments that are more widely used to correct pectus excavatum are the open technique or Ravitch procedure, and the minimally invasive repair technique or Nuss procedure. The Ravitch technique, described in 1949, consists in an open repair of the defect by a transverse inframammary incision, through which the malformed sternum and the costal cartilages are exposed. Through the anterior approach, costal cartilages are resected, preserving the perichondrium, and anterior sternal osteotomies are performed to correct the sternal depression defect. The wound is closed moving pectoral muscle flaps.

The minimally invasive surgery for pectus excavatum or Nuss procedure was described in 1998 by Dr. Donald Nuss. This technique allows the correction of the pectus excavatum without the need for a great incision in the skin or the resection of costal cartilages. In short, a lateral incision is performed in the thorax, through which, assisted by videothoracoscopy, a convex metal bar is inserted behind the sternum, which is exteriorized on the other side of the chest (Fig. 72.2). When the bar is flipped 180° the sternal defect pops up (Fig. 72.3). The bar is fixed to the ribs by stabilizers. This device is installed in the patient for 2–3 years.

Fig. 72.2

Insertion of the retrosternal bar

Fig. 72.3

Flipping of the retrosternal bar to pop out the sternal defect

Recently, a prospective, multicenter study was described in which the functional results were analyzed when correcting the pectus excavatum, whether by Ravitch technique or Nuss procedure. The results of this work show an important correction to Haller index and a significant improvement in the cardiac and pulmonary function tests (Table 72.2).

Table 72.2 Result of the surgical treatment of pectum excavatum

The complications of the surgical correction of pectus excavatum are uncommon, the most common being the displacement of the metallic devices, having to reoperate the patient to reposition the bar. Other more infrequent complications are wound infections, retrosternal hematomas, pneumothorax, hemothorax, myocardial lesions, and allergic reactions to metal. These complications tend to be more frequent after the Nuss procedure.

Pectus Carinatum

Pectus carinatum is the second most frequent congenital malformation of the costal wall. Like pectus excavatum, it is more frequent in men than in women, with a ratio of 4:1. It is more frequent to have a late consultation, because it tends to appear after age 11, worsening during puberty.

Preoperative Evaluation

Medical history and complete physical examination are necessary. The protrusion of the sternum with different morphologies will allow the classification of the malformation in its different types. Type 1 or chondrogladiolar is the one that protrudes in the gladiolus or sternal body and lower cartilages. Type 2 or chondromanubrial is less common. Here the manubrium sterni and the higher cartilages protrude. Type 3 or lateral deformities are those in which there is a unilateral protrusion or sternal rotation. There are also mixed forms. Most of the patients will not present symptoms, being mainly a cosmetic problem, which significantly influences the development of a negative body image. Some patients may report musculoskeletal pain in the thorax and epigastrium. The posteroanterior and lateral chest X-ray, and in some cases computerized tomography or magnetic resonance can be useful to have a surgical plan. Patients with a Haller index between 1.2 and 2.0 benefit from the correction of the deformity.

Treatment

Unlike pectus excavatum, the first line of treatment in pectus carinatum is the compressive therapy with orthosis according to the deformity type. In patients under 18 years of age, where the chest cavity is more malleable, the success rate varies between 65% and 80%. Dr. Marcelo Martínez-Ferro, a pediatric surgeon in Buenos Aires, developed a dynamic compression system that allows measuring the compression force electronically, with which he reports an 88% success rate (Fig. 72.4). Regarding the surgical treatment, it was initially described by Ravitch in 1952. The procedure is similar to the one for pectus excavatum, where the deformed costal cartilages are resected, keeping the perichondrium, and the sternal osteotomies are performed, depending on the type of information. Dr. Horacio Abramson, from Buenos Aires, published a paper in 2009 that described a minimally invasive technique to correct pectus carinatum. It is similar to the Nuss technique for pectus excavatum, but the bar goes through the sternum, allowing the retraction of the deformity (Fig. 72.5).

Fig. 72.4

Dynamic compression system. Dynamic compression system developed by Dr. Marcelo Martínez-Ferro

Fig. 72.5

Correction technique. Correction technique for pectus carinatum in a minimally invasive way developed by Dr. Horacio Abramson

Lung Surgery

Thoracotomy

Posterolateral thoracotomy is the classic way of accessing the thorax for the surgical treatment of lung lesions. The first lung lobectomy with anatomical dissection was performed in 1930. In 1941, Haight performed the first repair of an esophageal atresia in one stage through a left lateral thoracotomy. This kind of thoracotomy has an excellent access to the thorax, but to be able to perform it, the muscles of the costal wall (latissimus dorsi, trapezius, rhomboid, and serratus anterior) must be transected. It is associated with important adverse effects in the pediatric population, such as significant postoperative pain, winged scapula, alteration of the mobility of the shoulder, scoliosis and, cosmetically, a big scar.

Another technique for the open approach to the chest in the pediatric population is the thoracotomy with preservation of the muscle, described by Bianchi et al. in 1998. Kucukarslan et al. compared the results of the classic thoracotomy with that of muscle preservation. Regarding musculoskeletal deformities, the thoracotomy with preservation of the muscle significantly reduces the apparition of scoliosis (16% vs. 2.5%), shoulder elevation (30% vs. 7.5%), and winged scapula (38% vs. 12.5%). Besides, it significantly reduces the scale of pain and the hospitalization days.

Technique

The patient adopts the lateral decubitus position with a roll under the ribs to better open the intercostal spaces on the operation side. It is recommended to mark the important anatomical points before starting the surgery, as to have them as a reference during surgery (Fig. 72.6).

Fig. 72.6

Thoracotomy position

For the thoracotomy with preservation of the muscle, the place of the incision must be planned strategically to allow the most direct access to the pleural cavity. When the skin is opened, the latissimus dorsi and serratus anterior must be located. Then, the anterior edge of the latissimus dorsi is unlatched and retracted, exposing the serratus anterior, to which the posterior edge will be detached and retracted, exposing the intercostal space, accessing the pleural space through the fourth or fifth intercostal space. Once the surgery is finished, similar to the posterolateral thoracotomy, a pleural drainage is used; unlike the posterolateral thoracotomy, it is not necessary to close so many muscular planes.

Videothoracoscopy

Introduction

Thoracoscopy has been used since the early twentieth century. However, the development and miniaturization of instruments, such as video cameras, optical devices, and surgical and hemostasis equipment, has caused its popularity to grow exponentially over the past decades.

Nowadays, all thoracic pathologies in children are treated with a thoracoscopy approach, which has reduced postsurgical pain, recovery periods, and morbidity rates, as well as the long-term sequelae of these procedures (Table 72.3).

Table 72.3 Indications for pediatric thoracoscopy

In comparison with the open approach, thoracoscopy offers a superior exposure due to the visual magnification and closeness of the surgeon’s work area. Along with the lower morbidity rate of the minimally invasive procedures involved, this suggests that thoracoscopy should be the first-choice technique in virtually all thoracic procedures in children; however, we must recognize there is currently a lack of randomized studies supporting this proposal.

Preoperative Evaluation and Anesthetic Considerations

In general, both imaging studies, computerized axial tomography scan or magnetic resonance, provide guidance and can inform adequate planning for tackling most lesions.

The most important consideration when performing a thoracoscopy procedure in children is the creation of an actual space within the thorax which allows the surgeon to visualize and manipulate surgical instruments. This necessarily involves collapsing, at least partially, the ipsilateral lung. There is no specific preoperative test which may enable us to foresee if a child will tolerate mono-pulmonary ventilation. Nevertheless, most patients, even those with mechanical ventilation, will tolerate short periods of mono-pulmonary ventilation.

In order to achieve mono-pulmonary ventilation in children, patient size is a limiting factor. In patients over 30 kg, it is possible to use double lumen catheters in the same way as in adults. In smaller patients, it is possible to perform a selective bronchial blockage (Fig. 72.7). The bronchial blocker can even be used outside of the endotracheal tube and placed under bronchoscopy. In even smaller patients, when it is not possible to employ this technique, a selective mono-bronchial intubation can be performed, with a medium tube in a smaller size than the one advised for the patient. However, all these precautions may not be enough to obtain an adequate working space. In such cases, we can use a discrete CO₂ insufflation to the thorax, with low pressure and low current volumes, as a useful supplementary tool.

Fig. 72.7

Bronchial blocker

The positioning of the patient is key to achieve the best access to the lesion. In general, imaging techniques allow for an adequate planning for direct access, avoiding that any kind of tissue is interposed between the operator and the lesion. For example, a posterior mediastinum lesion is better faced with the patient in a semiprone position, making the lung fall forward. Similarly, when placing the patient and the trocars, care must be taken to maintain the eye-camera-monitor axis to facilitate the work of the surgeon. The same applies to the planning of a conversion to open surgery, if needed.

Finally, the postoperative care of these patients is not different from the usual handling of those with open thoracic surgery, having a better recovery due to the lower requirement of analgesics.

Dorsal Spine Surgery

Introduction

The pathological processes that can determine alterations in the child’s spine can be many: congenital or neuromuscular anomalies, alterations of bone development, skeletal dysplasias, traumatic, infectious, iatrogenic, or neoplastic pathologies, etc. It is basic to consider this heterogeneity regarding natural history, physiopathology, and comorbidities to formulate an adequate treatment. Additionally, regarding the child’s spine, the growing and developing dynamics will modulate the types and opportunities of the treatment.

Normal Development and Growth of the Spine

During the first three or four weeks of gestation the organogenesis takes place in concomitance with the formation of somites, mesenchymal molds for the future vertebrae. The appearance of a noxa in this developmental stage explains the coexistence of malformations in other organs in up to 30% of the cases, such as the central nervous system, and renal or cardiac systems. This is why it is important that patients with spine malformations have a multidisciplinary evaluation to detect and eventually treat these comorbidities.

Notwithstanding the cause of the deformity, its prognosis will greatly depend on its seriousness at the moment of the diagnosis and the growth potential that the child has. This is why it is of the utmost importance to know the critical and accelerated growth periods of the axial skeleton: the first occurs between birth and 3–4 years of age, and the second during the pubertal growth spurt. In these lapses, a longitudinal growth of 1.75–2 cm/year is produced in the segments of the spine, and it coincides with periods in which the progression of the deformities can accelerate, meriting more frequent checks.

Also very importantly, there is a delicate interdependence between the development of the chest cavity and spine with the development of the lung parenchyma. This can affect the respiratory function of the child and shorten their survival. The most crucial stage for this is the first five years of life, especially the two first years when more than 80% of the alveoli are formed, together with the growth of the dorsal spine and wall. Thus, any alteration that affects the development of the spine or the chest cavity can potentially generate not only a severe spinal deformity in the future but it can also determine a decrease in the definitive lung function, beyond the thoracic restriction. Thus, Campbell et al. defined the term thoracic insufficiency syndrome as the inability of the thorax to support normal ventilatory mechanics and lung growth. This is generally present in the context of patients with vertebral malformations and a complex thoracic wall, for whom an early spinal fusion has no benefit, because the lung function remains below normal (Fig. 72.8).

Fig. 72.8

Thoracic insufficiency syndrome. Patient of 2 years and 2 months of age, with multiple vertebral malformations and costal fusions, congenital left diaphragmatic hernia, without neurological or cognitive deficit, with recurring episodes of lung infection. (a) Total posteroanterior spine X-ray and (b) 3D reconstruction computerized axial tomography in posterior vision

Preoperative Evaluation

While it is not recommended to extrapolate the management between the different causes of spinal deformities, most of the indications of surgery in this age group are based on the projected risk, progression or worsening of the deformity, in the context of the natural history of its base pathology. This includes patients in whom the conservative corset management fails, and in whom a radiological progression is evident in the serialized monitoring. Even though it’s controversial, avoiding the progression of thoracic curves in patients with potential restrictive pathologies (e.g., muscular dystrophy) would have a protective effect in the long run, decreasing the speed of degeneration of the lung function. The reach of this measure has to be evaluated in conjunction with the morbidity associated with surgery and the natural progression of the condition. Finally, in some congenital malformation cases, the risk of neurological compromise is up to 12%, which reinforces the indication of surgery.

As has been previously stated, many of these children have a multisystem condition of which the spine is just a part. Additionally, the severe and rigid deformities they can have require wider and more invasive surgery. Thus, many of these children are exposed to a higher rate of perioperative complications regarding wound infection, pneumonia, implant failure, non-union, pseudoartrhosis, augmented blood loss, respiratory postoperative failure, and even death.

Owing to multiple presentations, in complex cases, the planning and preoperative preparation must be multidisciplinary and individualized. Associated anomalies and comorbidities must be anticipated and evaluated, such as cardiac, renal, and central nervous system malformations. A renal ultrasound scan is a simple and effective exam to evaluate urogenital malformations. If there is clinical suspicion, a referral to cardiology and an echocardiogram could discover interauricular or ventricular septum alterations, persistent ductus arteriosum, transposition of great vessels, lung stenosis, etc., among 10% and 26% of the congenital scoliosis cases. In patients with evidence of neurological deficit, it is recommended to request a magnetic resonance to rule out an intraspinal pathology, such as diastematomyelia, syringomyelia, or tethered spinal cord. In other cases, where the base pathology presents a high prevalence of anomalies of the central nervous system, the resonance is indicated independent from the physical exam. In patients with idiopathic scoliosis of the adolescent with normal neurological exam, the preoperative resonance is not indicated, because its efficacy would be under 3%.

The lung function can be altered in many of these patients, due to the precocious formation of the curve or the seriousness of the restrictive phenomenon. In these cases, it is essential to involve anesthesia and pediatric bronchopulmonary specialists, anticipating an eventually difficult airway and prolonged postoperative mechanical ventilation needs. Moreover, it must be considered that some of these children have vertebral cervical malformations (for example Klippel–Feil syndrome) that might make intubation difficult. This includes considering early pre or postoperative tracheostomy in cases with marginal lung function, especially taking into account that up to a 60% decrease is reported in spirometry tests in the postoperative of scoliosis surgery in some series. However, the use of noninvasive mechanical ventilation has lowered this indication and has enabled the performance of surgery in patients that were previously considered outside the reach of surgery. In cases where a thoracic insufficiency syndrome is suspected, and given the difficulties for spirometry tests in younger patients, the evaluation of the chest volume by a computerized axial tomography can be considered. This has been well correlated in studies with spirometry tests. Additionally, Gollogly et al. have published the volumes of normal lung parenchyma for the different ages and genders.

Other important aspects in the preoperative planning of these patients are the nutritional aspects, because regularly these patients present symptoms of protein–calorie malnutrition, whose presence has been correlated with postoperative results. Some of these cases are carriers of clotting or immunity alterations, having to plan beforehand the availability of the blood elements needed in each situation with the anesthesia team and the blood bank. The multidiscipline management needed for these complex patients must be stressed. The implementation of management algorithms coordinated among multiple disciplines for these patients’ preoperative stage has managed to diminish the general and ICU stay, along with a reduction in the rate of postoperative complications in some series.

Surgical Techniques

Traditionally, the most used technique to treat spinal deformities is the correction and instrumented spinal fusion. This was even applied for early start deformities (<5–10 years) under the precept that a short spine without a deformity was better than allowing the curve progression. However, it has recently been demonstrated that even early correction and fusion procedures that were considered successful result in the long term in a decrease of almost 50% of the FVC and FEV-1. Additionally, the frequent recurrence of deformities and the need of unplanned revision surgery have brought back the interest to develop systems that allow the correction of the curve but retain growth.

In generic terms these are called “growing” systems, and they are generally made through a posterior way of approach to the column. Owing to the enormous osteogenetic potential of children, the idea is not to touch the central zone with the instrumentation, latching only to the sides. Thus, the spontaneous fusion is avoided, placing the connective bars in subcutaneous or subfascial areas. These systems can be performed with a single bar or double bars connected with elongators. After the initial installation of the system, the periodic elongations only need to address this connective piece with the following minimization of surgery needed to produce growth (Fig. 72.9). The goal in general is to elongate until 10 years of age to later perform the definitive fusion. Another parameter to follow is to manage a T1–T12 > 18 cm longitude toward skeletal maturity. Values below these are associated to FVC below 45%.

Fig. 72.9

Spinal fixation with growing bars. Patient with DiGeorge syndrome that presents progressive scoliosis despite treatment with orthosis. A preoperative X-ray is presented (a), after the first surgery with the dual “growing” bars was performed (b), and after seven elongations in the space of four years (c). Note the progressive correction of the deformity and the increase of the longitude T1–T12

A separate mention has to be made for the VEPTR (Vertical Expandable Prosthetic Titanium Rib ) used mainly for congenital spine deformities associated with costal malformations and fusions, provoking chest insufficiency. In these cases, the elongation of the spine would not provoke the expansion of the compromised hemithorax, so an expansive thoracotomy, together with costal instrumentation, is also subject to be progressively elongated. However, all these “growing” systems share the same kind of disadvantages: need for multiple surgery procedures to produce “growth”, frequent complications, implant fractures, prominent instrumentation, considering that many of these patients are very small, the need to use a postoperative corset and the cost, among others. Although in general these complications are not serious, they happen in up to 48% of the cases, and they are more common when the surgeries start at a younger age. Given these factors, this group of patients is considered serious, and the controversy about the best treatment system persists.

In patients with severe progressive deformities around or after 10 years of age, the definitive correction and fusion is preferred. Although multiple ways to approach this exist (anterior, posterior, combined), the most used today is the instrumented (Fig. 72.10). With the development of modern column instrumentation and techniques, the ability to reduce and consolidate the deformities has increased up to 90%. The stability of definitive constructs has also eliminated the need for rest and postoperative orthosis. The morbidity derived from these procedures depends on the base pathology, being minimal for the adolescent idiopathic scoliosis and maximal for deformities in neuromuscular patients.

Fig. 72.10

Spinal fixation with fixed bars. Patient with type II spinal atrophy and severe neuromuscular scoliosis (Cob Index >100°). Preoperative (a) and postoperative (b) anteroposterior X-rays are shown. Note the typical pelvic obliqueness indicating neuromuscular scoliosis