BWH GENERAL SURGERY RESIDENCY … 1...BWH 2015 GENERAL SURGERY RESIDENCY PROCEDURAL ANATOMY COURSE 1. ANATOMICAL BASIS OF THORACIC SURGERY LAB OBJECTIVES After successfully completing

BWH 2015 GENERAL SURGERY RESIDENCY PROCEDURAL ANATOMY COURSE

1. ANATOMICAL BASIS OF THORACIC SURGERY

Contents Lab objectives ............................................................................................................................................... 2

Knowledge objectives ............................................................................................................................... 2

Skills objectives ......................................................................................................................................... 2

Preparation for lab ....................................................................................................................................... 2

1.1 BASIC PRINCIPLES OF ANATOMICAL ORGANIZATION ............................................................................ 4

1.2 THORACIC CAVITY AND CHEST WALL ..................................................................................................... 9

1.3 PLEURA AND LUNGS ............................................................................................................................. 13

1.4 ORGANIZATION OF THE MEDIASTINUM .............................................................................................. 19

1.5 ANTERIOR mediastinum ....................................................................................................................... 23

Thymus .................................................................................................................................................... 24

1.6 MIDDLE MEDIASTINUM (PERICARDIUM AND HEART)......................................................................... 25

Pericardium ............................................................................................................................................. 26

Heart external features .......................................................................................................................... 26

1.7 Superior mediastinum .......................................................................................................................... 27

Venous layer of the superior mediastinum ............................................................................................ 28

Arterial layer of the superior mediastinum ............................................................................................ 30

1.8 VISCERAL LAYER OF THE SUPERIOR AND POSTERIOR MEDIASTINUM ................................................ 32

1.9 LYMPH NODE STATIONS FOR LUNG CANCER STAGING ....................................................................... 33

1.10 POSTEROLATERAL THORACOTOMY ................................................................................................... 35

1.11 ANTEROLATERAL THORACOTOMY ..................................................................................................... 42

1.12 EMERGENCY LEFT ANTEROLATERAL THORACOTOMY....................................................................... 46

1.13 MEDIAN STERNOTOMY ...................................................................................................................... 58

1.14 SUBCLAVIAN ARTERY EXPOSURE ....................................................................................................... 62

BWH 2015 GENERAL SURGERY RESIDENCY PROCEDURAL ANATOMY COURSE


LAB OBJECTIVES After successfully completing Laboratory 1, you will be able to do the following.

Knowledge objectives 1. Explain four meanings of the term ligament. Describe the common features of the Scarpa fascia,

the ligament of Treitz, Gerota fascia, and cardinal ligaments of the uterus.

2. Describe the layers and organization of the chest wall, including bones, joints, intrinsic muscles, connective tissue layers, and neurovascular supply. Explain the primary anastomoses between the intercostal arteries, internal mammary arteries, and aorta.

3. Describe the topography of the pleural sacs and the specific terms used for various regions of the pleural sac. Explain the distinction between a pleural reflection and a pleural recess. Explain the distinction between the lung root and lung hilum. Describe the relative positions of the lung root structures on the hila of the left and right lungs.

4. Contrast the organization and composition of the two types of pericardium. Describe the pericardial sinuses and put your fingers in them. Describe the topography of the heart and the utility of the coronary sulcus, anterior interventricular sulcus, and posterior interventricular sulcus for locating the cardiac vessels. Explain three functions of the cardiac skeleton.

5. Explain the boundaries and basic organization of the mediastinum. Describe the structures located in the anterior mediastinum, middle mediastinum, superior mediastinum, and posterior mediastinum.

Skills objectives 1. Complete the anatomy lab equivalent of a posterolateral thoracotomy. 2. Complete the anatomy lab equivalent of an anterolateral thoracotomy. 3. Complete the anatomy lab equivalent of an emergency left anterolateral thoracotomy. 4. Complete the anatomy lab equivalent of a median sternotomy. 5. Complete the anatomy lab equivalent of an subclavian artery exposure.

PREPARATION FOR LAB Review this guide.

Watch the SCORE videos listed at the end of some procedures.

BWH ABS Lab 1. THORAX Page 1‐3

Figure 1‐1. Anatomical organization of the crus, axial view. (Modified from Netter Atlas of Human Anatomy, 5th Edition. Philadelphia: Elsevier, 2010.)



1.1 BASIC PRINCIPLES OF ANATOMICAL ORGANIZATION The basic principles of anatomical organization include the following.

Organization of superficial layers 1. Skin forms the outermost layer in all anatomical regions (Figures 1‐1, 1‐2, and 1‐3). Skin is the largest

body organ, accounting for approximately 8 to 10% of total body mass. Skin consists of an outer epidermis, composed of epithelium, and an inner dermis, composed of dense irregular connective tissue. Skin is continuous with the mucosa lining the respiratory, digestive, and urogenital systems; with the conjunctiva of the eye; and with the lining of the nasolacrimal duct. Skin lines the external auditory canal and forms the outer layer of the tympanic membrane.

2. Subcutaneous loose connective tissue supports skin function by providing thermal insulation, energy storage, and pathways for neurovascular structures serving skin but arising from larger nerves and vessels within deep fascial compartments. Subcutaneous loose connective tissue (subcutaneous fat, hypodermis, subcutis, superficial fascia) extends from the dermis to the deep investing fascia surrounding musculoskeletal compartments (Figures 1‐1 and 1‐2). All fat consists of adipocytes, collagen fibers, and elastin fibers. The proportions of the three components vary according to body region and local mechanical requirements. The subcutaneous fat of the hands and feet is very fibrous to resist local shear forces. Collagen fibers in subcutaneous fat form a distinct membranous layer variably present throughout the body. This membranous layer is described as Scarpa fascia over the anterior abdomen in contrast to the fatty Camper fascia forming the rest of the subcutaneous fat. It is present in all regions of the body, however, and may be confused with deep fascia.

3. An extensive network of superficial veins runs within the subcutaneous fat. In the limbs, the superficial veins receive blood from the skin and subcutaneous fat, drain through perforating tributaries to deep veins within the fascial compartments, and end by piercing the deep fascia to enter deep veins. Small cutaneous arteries usually arise as perforating branches of larger arteries supplying muscles within the fascial compartments. Cutaneous nerves often arise from large mixed nerves running within the fascial compartments. Lymphatic vessels draining superficial layers generally follow superficial veins to lymph node basins in the neck, axilla, and groin (inguinal region).

Organization of deep fascial compartments 4. Deep fascia, consisting of dense connective tissue, forms fascial compartments surrounding muscles,

bones, and joints in all body regions (Figure 1‐1 and 1‐1). Deep fascia is robust where it forms the investing deep fascia surrounding muscle groups in the limbs and neck and the masticatory muscles in the head. Deep fascia is thinner where it forms the investing fascia surrounding muscle groups in the shoulder, hip, trunk, and face. A layer of investing fascia, distinct from the epimysium surrounding individual muscles, always surrounds muscle groups in the head, limbs, and trunk.

In the limbs, investing deep fascia surrounds all muscle groups. Fascial septa connect the deep investing fascia with the periosteum of underlying bones, enclosing the muscle compartments of the limbs, and providing the anatomical basis of compartment syndrome. In the trunk, investing


Figure 1‐2. Anatomical organization of the thorax, axial view at the level of the L3‐L4 intervertebral disk. (Modified from Netter Atlas of Human Anatomy, 5th Edition. Philadelphia: Elsevier, 2010.)


deep fascia covers the outer surfaces of muscles, bones, and joints, and lining deep fascia covers the inner surface of the trunk wall, both the thoracic and abdominal surfaces of the diaphragm, and the pelvic surface of the pelvic sidewalls and pelvic floor muscles. In the abdominopelvic cavity, the lining fascia forms a continuous layer despite numerous regional name changes depending on the underlying muscle, so transversalis fascia is continuous with iliacus fascia, and diaphragmatic fascia, etc).

Organization of body cavities 5. Three meningeal layers surround the brain within the cranial cavity, and the spinal cord within the

vertebral canal. From superficial to deep, the meningeal layers are the dura mater, arachnoid mater, and pia mater. In the cranial cavity, the dura mater adheres firmly to the inner surface of the skull and the epidural space is a potential space occupied by the meningeal vessels, the most common source of cranial epidural hemorrhage. In the vertebral canal, the epidural space is an actual space, occupied by fat and the internal vertebral venous plexus. This actual space accommodates epidural anesthetic.

6. All nerves arise or terminate at the brain or spinal cord. Cutaneous nerves must pierce one or more layers of investing deep fascia to reach the skin and subcutaneous fat. Autonomic nerves supplying organs in the thoracic and abdominopelvic cavities must pierce the lining deep fascia of the anterior vertebral muscles to enter the mediastinum or retroperitoneum and reach those organs.

7. In the thoracic and abdominopelvic cavities, a layer of loose connective tissue intervenes between the lining deep fascia covering the inner surface of the trunk wall and the pleural or peritoneal sacs within the thoracic and abdominopelvic cavities. Opening this loose connective tissue layer provides extrapleural or extraperitoneal access.

In the thoracic cavity, the extrapleural loose connective tissue (endothoracic fascia) anchors the parietal pleura to the chest wall and diaphragm and condenses to bridge the aperture between the first rib, sternum, and first thoracic vertebra as the suprapleural membrane (of Sibson). The extrapleural loose connective tissue of the chest wall is continuous with the loose connective tissue surrounding organs and vessels in the mediastinum.

In the abdominopelvic cavity, the extraperitoneal loose connective tissue (endoabdominal fascia, preperitoneal fascia, preperitoneal fat) is continuous with the loose connective tissue surrounding organs and vessels in the retroperitoneum, with the visceral fat occupying spaces within the mesenteries, omenta, and peritoneal ligaments of the abdominal cavity, and with the visceral fat filling the spaces around the infraperitoneal pelvic viscera.

Like subcutaneous fat, visceral fat consists of adipocytes, collagen fibers, and elastin fibers, and the proportions of the three tissue components vary according to regional and local mechanical requirements. Many fibrous condensations of visceral fat, often containing smooth muscle fibers, are designated eponymous fasciae or ligaments. Examples are the ligament of Treitz, the Gerota fascia surrounding the perirenal fat and kidney, and the cardinal ligaments of the uterus. Smooth muscle fibers are also found within the fat of the greater omentum.

8. All vessels and their major branches ultimately arise or terminate at the heart within the media‐stinum or at the aorta or inferior vena cava within the retroperitoneum. Visceral fat continuous with mediastinal or retroperitoneal fat accompanies blood vessels as they travel throughout the body. As large vessels leave the thoracic or abdominopelvic cavities, a layer of lining deep fascia is


Figure 1‐3. Anatomical organization of the abdomen, axial view at the level of the L3‐L4 intervertebral disk. (Modified from Netter Atlas of Human Anatomy, 5th Edition. Philadelphia: Elsevier, 2010.)


prolonged over the vessels,e ventually blending with their adventitiae. Examples of these lining fascial prolongations are the axillary sheath and the femoral sheath.

9. The paired pleural sacs and single peritoneal sac are closed mesothelial sacs, normally containing only a thin layer of serous fluid. The surfaces of the closed sacs are termed visceral where they cover the external surfaces of organs, and parietal where they face the inner surfaces of the thoracic wall, abdominal wall, or diaphragm, or where the form the lateral partitions of the mediastinum.

Pleural or peritoneal reflections are regions where the mesothelium over an organ or parietal surface turns a corner, and continues on another surface. Pleural or peritoneal recesses are the regions within the closed sacs that correspond to the pleural or peritoneal reflections. Pleural or peritoneal ligaments and peritoneal omenta or mesenteries are formed where two layers of mesothelium surround neurovascular structures and visceral fat travelling from the mediastinum or retroperitoneum to the thoracic or abdominopelvic organs.

In the thoracic cavity, the basic pleural terminology is expanded by adjectives differentiating regions of parietal pleura. Examples are the costal parietal pleura, diaphragmatic parietal pleura, mediastinal parietal pleura, and cervical parietal pleura on the internal surface of the suprapleural membrane.

In the abdominopelvic cavity, the basic peritoneal terminology is expanded by special terms for what are generically peritoneal ligaments. Examples are the mesenteries running from the parietal peritoneum covering the retroperitoneum to the bowel, the falciform ligament running from the anterior abdominal wall to the liver, the lesser omentum running from the liver to the lesser curvature of the stomach, and the greater omentum running from the greater curvature of the stomach to the parietal peritoneum covering the retroperitoneum.

During embryonic development, the rapidly elongating intestines pressed the duodenum, right colon, and left colon firmly against the posterior abdominal wall. Subsequently, the visceral peritoneum covering these organs and their mesenteries fused with the parietal peritoneum separating the peritoneal space from the retroperitoneum. The fixed portions of the gastrointestinal tracts are separated from the retroperitoneal fat and organs by fusion planes, despite unhelpful organ descriptions such as `secondarily retroperitoneal’. These peritoneal fusion planes may be opened, and the fixed organs and their mesenteries mobilized, to create ‘bloodless’ surgical access planes.

It is worth noting that the term ligament, is used to refer to a wide variety of functionally and mechanically disparate anatomical structures, and similar considerations apply to the term fascia.. Structures referred to as ligaments include:

The robust ligaments reinforcing the joints of the musculoskeletal system such as the collateral ligaments of hinge joints.

Pleural or peritoneal ligaments such as the pulmonary ligament between the mediastinal parietal pleura and lung visceral pleura and the falciform ligament.

Fibrous condensations of visceral fat such as the ligament of Treitz and cardinal ligament of the uterus.

BWH ABS Lab 1. THORAX Page 1‐9 Adult vestiges of embryonic structures such as the round ligament (a vestige of the umbilical vein)

within the falciform ligament (a double‐layered peritoneal reflection).

Figure 1‐4. Chest wall bones and joints. (Modified from Netter Atlas of Human Anatomy, 5th Edition. Philadelphia: Elsevier, 2010.)


1.2 THORACIC CAVITY AND CHEST WALL Thoracic cavity The thoracic cavity is the space enclosed by the bones, joints, intrinsic muscles, and fascia of the chest wall (Figure 1‐1). The thoracic cavity surrounds the left and right pleural sacs and the mediastinum, the central region between the two pleural sacs (Figure 4‐1).

The thoracic outlet refers to the superior thoracic aperture framed by the manubrium, the first pair of ribs, and T1 vertebra. The inferior thoracic aperture, framed by the xiphisternal junction, costal margin, and T12 vertebra, is closed by the dome‐shaped diaphragm, a skeletal muscle. Both the superior and inferior thoracic outlets are sharply convex. The lung apices extend superiorly into the neck. The liver and stomach lie beneath the inferior portions of the ribs.

Chest wall bones and joints The thoracic wall consists of a jointed bony cage (Figure 1‐4) with intercostal muscles filling the spaces between the ribs laterally, and the diaphragm closing the thoracic cavity inferiorly. Contraction of the intercostal muscles and diaphragm produce motion at the joints between the ribs and vertebrae posteriorly at the costovertebral and costotransverse joints and anteriorly at the costosternal joints. During inhalation, the ribs swing laterally and anteriorly.


Figure 1‐5. Chest wall intrinsic and extrinsic muscles. (Modified from Netter Atlas of Human Anatomy, 5th Edition. Philadelphia: Elsevier, 2010.)

BWH ABS Lab 1. THORAX Page 1‐12 Chest wall intrinsic and extrinsic muscles

Except for a very small area at the triangle of auscultation posteriorly, the intrinsic muscles of the chest wall (intercostal muscles) are completely covered by the posterior shoulder muscles, anterior shoulder muscles, and anterior abdominal muscles (Figure 1‐5). Consequently, thoracotomy incisions may necessitate division of the pectoralis major or minor, latissimus dorsi, or serratus anterior muscles.

The intrinsic muscles of the trunk wall comprise a trilaminar muscle plywood surrounded by deep fascia, and very similar in both thorax and abdomen.

The external intercostal muscles form the outer layer of chest wall muscles. Anteriorly, fibers in this muscle layer run inferomedially. Deep investing fascia covers the outer surfaces of the intercostal muscles and blends with the periosteum of the intervening ribs.

The internal intercostal muscles form the intermediate layer of chest wall muscles.

The innermost layer of chest wall muscles is discontinuous, consisting of the transversus thoracis muscles anteriorly, the innermost intercostal muscle laterally, and the subcostal muscles posteriorly. A layer of deep lining fascia lies between the innermost muscle layer of the chest wall and the underlying endothoracic fascia.

A layer of fibrous loose connective tissue, the extrapleural connective tissue (endothoracic fascia) lies between the deep lining fascia of the trunk wall and the costal parietal pleura. The extrapleural connective tissue binds the parietal peritoneum to the chest wall. Superiorly, the endothoracic fascia condenses to form the suprapleural membrane (of Sibson) superior to the cervical parietal pleura. Medially, the extrapleural connective tissue is continuous with the loose connective tissue of the mediastinum.

Chest wall innervation The pattern of chest wall innervation is entirely segmental. Each intercostal or thoracoabdominal nerve supplies a strip of skin, muscle, fascia, and parietal pleura derived from an embryonic myotome and dermotome.

The intercostal nerves supplying the chest wall run between the internal intercostal and innermost intercostal muscles. Anterior cutaneous and lateral cutaneous branches leave the intercostal nerves to pierce overlying layers and reach the skin.

Chest wall blood supply The pattern of trunk wall blood supply includes both segmental horizontal and vertical anastomoses. In any anastomosis, arterial or venous, interruption of flow from one arterial source can be mitigated by reversal of flow from another source.

Each intercostal artery consists of a posterior intercostal portion from the aorta and an anterior intercostal portion from the internal mammary artery. Medially, the internal mammary artery, a branch of the axillary artery, continues inferiorly as the superior epigastric artery and anastomoses with the inferior epigastric artery, a branch of the external iliac artery.

The intercostal veins follow a similar pathway, draining anteriorly into the internal mammary veins and posteriorly into the azygos/hemiazygos venous network.


Figure 1‐6. Pleura (upper image). (Modified from Netter Atlas of Human Anatomy, 5th Edition. Philadelphia: Elsevier, 2010.) Supine chest film of a patient with right tension pneumothorax and `deep sulcus sign’ (lower image. (Modified from the New England Journal of Medicine Image Challenge, http://www.nejm.org.


1.3 PLEURA AND LUNGS Pleura The left and right pleural sacs each consist of a continuous layer of mesothelium, the pleura. The terms for different regions of the pleural sacs describe the surfaces they attach to (Figure 1‐6). Visceral pleura covers the external surface of the lung. Costal parietal pleura covers the internal surface of the chest wall. Diaphragmatic parietal pleura covers the thoracic surface of the diaphragm. Mediastinal parietal pleura forms the lateral boundaries of the mediastinum. Cervical parietal pleura extends superior to the first rib into the base of the neck, roofing the space between the first ribs, the sternum, and the T1 thoracic vertebra. Extrapleural connective tissue attaches the parietal pleura firmly to the underlying surface. Subpleural connective tissue attaches the visceral pleura to the lung and provides a pathway for lymphatic channels.

Pleural reflections are corners where parietal pleura leaves one surface to continue onto another surface. Examples of pleural reflections are the costodiaphragmatic reflection and the costomediastinal reflection (Figure 1‐6 lower image).

The lung root consists of a mainstem bronchus, pulmonary artery, and two pulmonary veins). At the lung root, the mediastinal parietal pleura reflects laterally and becomes continuous with the visceral pleura covering the lung root and lung itself. Inferior to the lung root, the anterior and posterior reflections of the mediastinal pleura form the left and right pulmonary ligaments, a double layer of pleura surrounding a layer of connective tissue and lymphatic vessels (Figure 1‐7, next page).

The left and right pleural spaces (cavities) lie between the parietal and visceral surfaces of the left and right pleural sacs. The pleural space normally contains only a thin layer of lubricating pleural fluid that reduces friction between the adjacent pleural surfaces during respiratory movement. The surface tension of the pleural fluid also secures the close apposition between adjacent surfaces of parietal and visceral pleura so that the external surfaces of the lungs are drawn outward as the thoracic cavity expands. Similarly, quiet exhalation occurs without muscular activity when elastic recoil of the lung connective tissue draws the thoracic cavity inward to its resting position.

Pleural recesses (Figure 1‐6) are those areas of the pleural space extending into the pleural reflections. Even during deep inspiration, the lungs never completely fill the pleural recesses.

Pleural fluid normally consists of a thin transudate within the pleural sac. Pleural fluid transudation and pleural fluid reabsorption are normally balanced. A pleural effusion may be either accumulation of excessive transudate (hydrothorax), resulting from altered Starling forces, or an exudate resulting from microvascular damage and leakage of plasma proteins into the interstitial space and pleural fluid.


Figure 1‐7. Left and right lungs, mediastinal surface. (Modified from Netter Atlas of Human Anatomy, 5th Edition. Philadelphia: Elsevier, 2010.)

BWH ABS Lab 1. THORAX Page 1‐16 Lungs

The lungs are roughly pyramidal in shape, each consisting of a blunt apex, a concave base, a convex costal surface, and a irregularly concave mediastinal surface. The lung apices extend superior to the thoracic inlet for 2 to 5 cm. The concave bases of the lungs follow the curvature of the dome‐shaped diaphragm. The medial surface of each lung presents a vertebral part and a mediastinal part which includes the pulmonary hilum, the region of the lung where the lung root structures (bronchi, pulmonary vessels) enter and leave the lung. Although the lungs are paired organs, they are asymmetrical in terms of size, shape, and lobation.

Lobes. The left lung has two lobes (superior lobe and inferior lobe) separated by the left oblique fissure. The right lung has three lobes (superior lobe, middle lobe, and inferior lobe). The right oblique fissure separates the superior and middle lobes from the inferior lobe. The shorter horizontal fissure separates the right superior and middle lobes from one another. Each pulmonary lobe is ventilated by a lobar bronchus (Figure 4‐3) and perfused by a lobar artery (Figure 4‐4).

Lung root and hilum


Figure 1‐8. Left and right lungs, mediastinal surface. (Modified from Netter Atlas of Human Anatomy, 5th Edition. Philadelphia: Elsevier, 2010.)

BWH ABS Lab 1. THORAX Page 1‐18 Bronchopulmonary segments. The lung lobes are further subdivided into bronchopulmonary segments (Figure 1‐8). Each segment consists of a pyramidal section of lung tissue ventilated by a segmental bronchus and perfused by a segmental artery adjacent to the segmental bronchus. Blood and lymph from the bronchopulmonary segments drain through intersegmental veins and lymphatic vessels running between segments. Pulmonary (N1) nodes lie along the path of the airway and pulmonary vessels, often tucked into branching points.


Figure 1‐9. Organization and divisions of the mediastinum according to the classic four‐compartment model (A), the three compartment model according to (Townsend 2012) and (Mulholland 2010) (B), and the three‐compartment model according to (Burkell 1969) and (Brunicardi 2009) (C).


1.4 ORGANIZATION OF THE MEDIASTINUM The term mediastinum refers to the region of the thoracic cavity between the left and right pleural sacs (Figure 5‐1). All thoracic viscera except the lungs and lung roots (bronchi and vessels entering and leaving the lung hilum) lie within the mediastinum.

Nestled within the visceral fat of the mediastinum are the thymus or thymic remnants; the heart, the pericardium, the great vessels entering and leaving the heart; the trachea and extrapulmonary portions of the main bronchi; the esophagus; the thoracic duct; and many lymph node stations. The thoracic portions of the left and right vagus nerves, the left recurrent laryngeal nerve, the thoracic sympathetic trunks, the thoracic splanchnic nerves, and the autonomic cardiac and pulmonary plexuses also lie within the mediastinum. The phrenic nerves supplying the diaphragm run within the mediastinum just medial to the mediastinal parietal pleura superiorly and between the mediastinal parietal pleura and fibrous pericardium inferiorly.

Boundaries and divisions of the mediastinum. The boundaries of the mediastinum are the thoracic inlet superiorly, the diaphragm inferiorly, the sternum and costal cartilages anteriorly, the mediastinal parietal pleura laterally on both sides, and the ribs and thoracic vertebrae posteriorly.

According to the classic four‐compartment model of the mediastinum (Figure 5‐1 A), a horizontal plane passing through the sternal angle, superior limit of the fibrous pericardium, and T4 vertebral body divides the mediastinum into the superior mediastinum and inferior mediastinum. The dense fibrous pericardium surrounding the heart further divides the inferior mediastinum into the anterior mediastinum, middle mediastinum, and posterior mediastinum, with the fibrous pericardium forming the outer boundary of the middle mediastinum. Except for an arbitrary horizontal plane, therefore, the superior mediastinum is continuous with both the anterior and posterior mediastinum and many mediastinal structures occupy more than one mediastinal division.

The continuities among mediastinal structures are more evident in variations on the three‐compartment model. In Figure 5‐1 B (Townsend 2012 and Mulholland 2010), the middle (visceral) mediastinum extends superiorly to the thoracic outlet. In Figure 5‐1C (Burkell 1969 and Brunicardi 2009), the fibrous pericardium is the superior limit of the middle (visceral) mediastinum and the anterior and superior mediastina comprise a single division.


Figure 1‐10. Left thoracic cavity, left pleural space, and left mediastinum, left lung removed. (Modified from Netter’s Atlas of Human Anatomy, 5th Edition. New York: Elsevier, 2010.)


Figure 1‐11. Right thoracic cavity, right pleural space, and right mediastinum, right lung removed. (Modified from Netter’s Atlas of Human Anatomy, 5th Edition. New York: Elsevier, 2010.)


Figure 1‐12. Thymus. (Modified from Netter Atlas of Human Anatomy, 5th Edition. Philadelphia: Elsevier, 2010.)


1.5 ANTERIOR MEDIASTINUM The anterior mediastinum is located between the sternum anteriorly and the fibrous pericardium and superior mediastinum posteriorly. The thymus, sternopericardial ligaments, and lymph nodes and lymphatic vessels occupy the anterior mediastinum

Thymus Organization. The thymus consists of left and right lobes. Each lobe consists of an outer cortex and an inner medulla surrounded by a connective tissue capsule. A central connective tissue septum, continuous with the capsule, unites the two thymic lobes. The thymus achieves its maximum relative size in children and its maximum absolute size in adolescents. The thymus remains functional throughout life, but undergoes progressive fatty involution after adolescence.

Position and relations. The thymus extends superiorly to the thyroid gland and inferiorly to the fibrous pericardium. In the elderly, the lateral boundaries of the thymus are difficult to distinguish from fat. The thymus lies anterior to the trachea, brachiocephalic veins, and fibrous pericardium.

Development. The thymic parenchyma develops in the neck from third pharyngeal pouch endoderm in common with the inferior parathyroid glands. During its descent into the chest, the thymus may drag the inferior parathyroid glands into an ectopic location in the anterior mediastinum.

Neurovasculary supply. Small branches of the internal mammary and inferior thyroid arteries supply the thymus. Between one and four small thymic veins drain into the brachiocephalic veins and internal mammary veins. Lymph from the thymus drains to brachiocephalic, tracheobronchial, and parasternal lymph nodes.


Figure 1‐13. Left thoracic cavity, left pleural space, and left mediastinum, left lung removed. (Modified from Netter’s Atlas of Human Anatomy, 5th Edition. New York: Elsevier, 2010.)


1.6 MIDDLE MEDIASTINUM (PERICARDIUM AND HEART) Pericardium

The pericardium consists of an outer fibrous pericardium, consisting of dense connective tissue and surrounding a continuous, closed mesothelial sac, the serous pericardium (Figure 1‐13). Like the pleural sac and pleural space, the serous pericardial sac encloses the pericardial space and changes its name as it covers different surfaces. The parietal serous pericardium lines, and fuses with, the internal surface of the fibrous pericardium. The visceral serous pericardium (epicardium) covers the external surface of the heart. The pericardial space (cavity) which normally contains only a thin layer of pericardial fluid.

Like the pleural space (cavity), the pericardial space has recesses—regions within pericardial reflections where the serous pericardium leaves one surface, turns a corner, and continues on another surface. The oblique pericardial sinus and transverse pericardial sinus are named recesses within the pericardial space. A broad unnamed recess is also formed where the parietal serous pericardium leaves the fibrous pericardium superiorly and reflects onto the great vessels (Figure 1‐14, next page).

Heart external features The heart is a muscular pump maintaining blood flow through both the pulmonary (right heart) and the systemic (left heart) circuits simultaneously (Figure 1‐13).

The right atrium receives deoxygenated systemic blood from the superior and inferior venae cavae, the coronary sinus, and small thebesian veins draining the heart wall, and delivers deoxygenated blood to the right ventricle through the right atrioventricular (tricuspid) valve. The right ventricle pumps deoxygenated blood to the lungs through the pulmonary arterial trunk.

The left atrium receives oxygenated blood from the lungs through four pulmonary veins, and delivers oxygenated blood to the left ventricle through the left atrioventricular (mitral) valve. The left ventricle pumps oxygenated blood to systemic circulation through the aorta.

The coronary sulcus is an indentation marking the boundary between the atria and ventricles and indicating the plane of the heart fibrous skeleton and heart valve annuli. The anterior interventricular sulcus and posterior interventricular sulcus lie perpendicular to the coronary sulcus, mark the boundary between the ventricles, and indicate the plane of the interventricular septum.

The coronary and interventricular sulci are useful landmarks for locating the coronary arterial supply and venous drainage of the heart.

The fibrous skeleton of the heart, resembling a pretzel, consists of three dense fibrous rings surrounding the left and right atrioventricular valves and the aortic valve. The rings are joined centrally by a fibrous trigone. The fibrous skeleton of the heart serves simultaneously as an attachment for cardiac muscle fibers, as a structural support and attachment for the valve cusps, and as an insulator preventing depolarization of atrial muscle fibers from spontaneously initiating depolarization of ventricular muscle fibers. The atrioventricular bundle (of His) passes through the fibrous skeleton and interventricular septum to the heart apex where ventricular systole begins.


Figure 1‐14. Venous layer of the superior mediastinum (A) and right (blue) side of the mediastinum. (Modified from Netter’s Atlas of Human Anatomy, 5th Edition. New York: Elsevier, 2010.)


1.7 SUPERIOR MEDIASTINUM Structures in the superior mediastinum occupy three layers: 1) a venous layer consisting of the superior vena cava and its tributaries, 2) an arterial layer consisting of the aorta and its branches, and 3) a visceral layer consisting of the trachea, esophagus, and other important structures.

Venous layer of the superior mediastinum The superior vena cava tis formed by the confluence of the right and left brachiocephalic veins (Figure 1‐14). Each brachiocephalic vein is formed by the confluence of the internal jugular vein and subclavian vein. The thoracic duct typically enters the left brachiocephalic vein at this confluence. The right lymphatic duct typically enters the right brachiocephalic vein.

The azygos vein receives blood from the chest wall and drains into the superior vena cava). The variable system of hemiazygos and accessory hemiazygos veins also receive blood from the chest wall and drain into the azygos vein or left subclavian vein. The inferior portion of the azygos vein often lies obliquely across the posterior mediastinum.


Figure 1‐15. Arterial layer of the superior mediastinum. (Modified from Netter’s Atlas of Human Anatomy, 5th Edition. New York: Elsevier, 2010.)


Arterial layer of the superior mediastinum The arterial layer of the superior mediastinum includes the ascending aorta, aortic arch, and proximal portion of the descending aorta, and the pulmonary trunk and its left and right pulmonary arteries.

Textbook descriptions of the path of the left vagus nerve in the superior mediastinum are often misleading, confusing, or both. In fact, the left vagus nerve descends along the lateral surface of the aortic arch to reach the esophagus. The left recurrent laryngeal nerve leaves the left vagus nerve, passes medially by running inferior to the aortic arch and posterior to the ligament arteriosum, then runs superiorly in the interval between the trachea and esophagus.


Figure 1‐16. Visceral layer of the middle mediastinum. (Modified from Netter’s Atlas of Human Anatomy, New York: Elsevier, 2010.)


1.8 VISCERAL LAYER OF THE SUPERIOR AND POSTERIOR MEDIASTINUM The visceral layer of the superior mediastinum contains the trachea and bronchi, esophagus, mediastinal lymph nodes, and the cardiac and pulmonary autonomic nerve plexuses. Structures located in both the visceral layer of the superior mediastinum and the posterior mediastinum include the esophagus, the descending aorta and its branches, and the azygos and hemiazygos veins and their tributaries (Figure 5‐21).


Figure 1‐17 Lymph node stations for lung cancer staging, generally following Townsend, 2012. (Modified from Netter’s Atlas of Human Anatomy, 5th Edition. New York: Elsevier, 2010).


1.9 LYMPH NODE STATIONS FOR LUNG CANCER STAGING N1 lymph nodes (stations 10 through 14) are located within pulmonary tissue, often at airway branch points. The interlobar nodes (11R, 11L), comprising the lymphatic sump of Borrie, receive lymphatic drainage from all lobes of the ipsilateral lung. The hilar (bronchopulmonary) (10R,10L) nodes are located at the lung hilum near the entry of the lung root structures.

N2 lymph nodes (stations 1 through 9) are located in the mediastinum. Lymphatic vessels from nodes in the superior mediastinum converge to form left and right bronchomediastinal lymphatic trunks. The bronchomediastinal lymphatic trunks usually enter the brachiocephalic veins directly, but they may also enter the thoracic duct or right lymphatic duct, respectively.

Lymph from the right lung drains to ipsilateral N2 nodes. Lymph from the superior lobe of the left lung generally drains to ipsilateral N2 nodes. Lymph from the inferior lobe of the left lung generally drains to contralateral (right) N2 nodes.


Figure 1‐18. Posterolateral thoracotomy. (From Sugarbaker DJ, Bueno R Krasna MJ, Mentzer SJ, Zellos L, Adult Chest Surgery, 2nd Edition. McGraw‐Hill Professional, 2015.


1.10 POSTEROLATERAL THORACOTOMY

POSTEROLATERAL THORACOTOMY a. Patient is placed in a standard lateral decubitus position, with the ipsilateral arm extended forward b. Inferior tip of scapula is palpated and marked c. Incision begins approximately 3cm posterior to the scapula tip and approximately halfway between

the scapula and the spinous process


POSTEROLATERAL THORACOTOMY (continued) d. The incision curves around the tip to lie along the top margin of the sixth rib (5th ICS), extending to

anterior axillary line

e. Scarpa’s fascia, latissimus dorsi muscle are divided. Serratus anterior muscle can be spared by freeing it and rotated forward.


POSTEROLATERAL THORACOTOMY

Left lateral thoracotomy (Figure 1‐20, C and D).

Through the left posterolateral thoracotomy incision, retract the left lung posteriorly.

Identify the thin mediastinal parietal pleura. Identify the left phrenic nerve and pericardiacophrenic vessels where they run between the mediastinal parietal pleura and the fibrous pericardium.

Retract the left lung anteriorly and identify the structures comprising the lung root, the left pulmonary artery, left main bronchus, and inferior pulmonary vein.

Identify the descending aorta.

Right lateral thoracotomy (Figure 1‐20 A and B).

Through the right posterolateral thoracotomy incision, retract the right lung posteriorly.

Identify the thin mediastinal parietal pleura. Identify the right phrenic nerve and pericardiaco‐phrenic vessels where they run between the mediastinal parietal pleura and the fibrous pericardium.

Identify the azygos vein. Follow the azygos vein to the inferior vena cava. Identify the right pulmonary artery, and superior pulmonary vein.

Retract the right lung anteriorly and identify the azygos vein. Identify the right main bronchus and inferior pulmonary vein.

Identify the right main bronchus and inferior pulmonary vein.

Identify the esophagus.


Figure 1‐21. Anterolateral thoracotomy. (From Sugarbaker DJ, Bueno R Krasna MJ, Mentzer SJ, Zellos L, Adult Chest Surgery, 2nd Edition. McGraw‐Hill Professional, 2015.


1.11 ANTEROLATERAL THORACOTOMY

ANTEROLATERAL THORACOTOMY Elective setting, pulmonary resections, etc Mario Aycart, MD

a. Patient placed in lateral decubitus position. Arm placed in classic “swimmer” position with 90‐degree abduction of the upper arm to allow easier access to 4th ICS.

b. Incisions generally are placed in 4th or 5th ICS. Starting approximately 1cm posterior to pectoralis major muscle and runs along the top of the rib for 10‐15cm.


Figure 1‐22 Anterolateral thoracotomy. (From Sugarbaker DJ, Bueno R Krasna MJ, Mentzer SJ, Zellos L, Adult Chest Surgery, 2nd Edition. McGraw‐Hill Professional, 2015.


ANTEROLATERAL THORACOTOMY (continued) Mario Aycart, MD

c. Skin and scarpa’s fascia divided. d. Serratus anterior divided along the course of its fibers and not rotated


Figure 1‐23. Emergency left anterolateral thoracotomy. (From Mattox KL, Moore EE, Feliciano DV, Trauma, 7th Edition. McGraw‐Hill Professional, 2015.


1.12 EMERGENCY LEFT ANTEROLATERAL THORACOTOMY

EMERGENCY LEFT ANTEROLATERAL THORACOTOMY: Emergency Department Resuscitative Thoracotomy (EDRT)

Mario Aycart, MD

Upon patient arrival and determination of the need for EDT, the patient’s left arm should be placed above the head to provide unimpeded access to the left chest.

Set‐up (real situation) should include:

10‐blade scalpel

Finochietto’s chest retractor

Toothed forceps

Curved Mayo’s scissors

Satin‐sky’s vascular clamps (large and small)

Long needle holder

Lebsche’s knife and mallet

Internal defibrillator paddles

Sterile suction

Skin stapler

Access to a variety of sutures should be available (specifically 2‐0 prolene on a CT‐1 needle, 2‐0 silk ties, and teflon pledgets)

a. Antiseptic solution splashed on the chest, though skin prep is not required b. Incision made in the 5th or 6th ICS (*have seen described 4‐6th ICS), starting from costochondral

junction anteriorly and passing to the mid‐axillary line laterally, following the upper border of the rib



Mario Aycart, MD

c. Skin and subcutaneous layer are first incised with a No.10 blade and then the muscle, periosteum, and parietal pleura are divided in one layer with scissors and blunt dissection.

d. Chest wall retractor inserted (e.g., Finochietto) with handle pointing towards the axilla for ease of instrumentation and visibility.



Mario Aycart, MD

e. Costochondral junctions of the 5th, 4th and sometimes 3rd rib are divided quickly for greater exposure

f. Confirm ET intubation g. Control hemorrhage h. Relief of cardiac tamponade if present – pericardium is opened anterior and parallel to the phrenic

nerve. Hemopericardium evacuated.



Mario Aycart, MD

i. Cardiac injury controlled with digital pressure. With a beating heart, any attempt at repair should be delayed until initial resuscitative measures are completed. In the case of a non‐beating heart, suturing may be performed before resuscitation and defibrillation.

j. Effective cardiac compression



Mario Aycart, MD

k. Cross‐clamping the pulmonary hilum in the case of major lung hemorrhage, air embolism, or massive bronchopleural fistula



Mario Aycart, MD

l. Cross‐clamping of the descending aorta (DA) for lower torso hemorrhage control and for temporary increase in the proximal arterial pressure and hence preservation of perfusion of the brain and heart.

i. DA is occluded inferior to the left pulmonary hilum, which is best exposed by elevation of the left lung anteriorly and superiorly.

ii. The aorta must be separated from the esophagus anteriorly and the pre‐vertebral fascia posteriorly by blunt dissection, before occluding using a large vascular clamp, such as a DeBakey.

INDICATIONS:

Salvageable postinjury cardiac arrest:

Patients sustaining witnessed penetrating thoracic trauma with


Figure 1‐29. Median sternotomy. (From Sugarbaker DJ, Bueno R Krasna MJ, Mentzer SJ, Zellos L, Adult Chest Surgery, 2nd Edition. McGraw‐Hill Professional, 2015.


1.13 MEDIAN STERNOTOMY MEDIAN STERNOTOMY Mario Aycart, MD

a. Supine with transverse roll beneath the most kyphotic portion of back b. Sternal notch and tip of xiphoid marked and marking of midline of sternum


Figure 1‐30 . Median sternotomy. (From Sugarbaker DJ, Bueno R Krasna MJ, Mentzer SJ, Zellos L, Adult Chest Surgery, 2nd Edition. McGraw‐Hill Professional, 2015.


MEDIAN STERNOTOMY Mario Aycart, MD

c. Skin incision should extend from the sternomanubrial junction to 2cm below the tip of the xiphoid. d. Dissection is carried down through Scarpa’s fascia between the origins of the two pectolaris major

muscles. Extended above sternal notch.

e. Divide the clavicular‐clavicular ligament f. Linea alba is divided for 2cm caudal to the tip of xiphoid process g. Bluntly dissect tissue away from behind sternum superiorly (manubrium) and inferiorly (xiphoid‐

linea alba)

h. Saw footplate placed deep to bone and proceeds superior to inferior in the center in careful, steady fashion

i. Hemostasis achieved by cauterizing the edges of the periosteum and the application of either bone wax or topical coagulant (thrombin‐soaked gelfoam).

j. Sternal retractor is placed

Video: http://www.surgicalcore.org/videoplayer/510000060/50


Figure 1‐31. Subclavian artery exposure. (Modified from Netter Atlas of Human Anatomy, 5th Edition. Philadelphia: Elsevier, 2010.)


1.14 SUBCLAVIAN ARTERY EXPOSURE

SUBCLAVIAN ARTERY EXPOSURE a. Short transverse supraclavicular incision between the two heads of the SCM extending lateral to the

clavicular head of SCM

b. Platysmal flaps are raised with care taken to avoid trauma to the EJV. c. SCM is retracted medially d. Omohyoid is divided and common carotid artery is circumferentially dissected and mobilized

medially

e. If left sided exposure, the thoracic duct is identified and ligated. f. The IJV and vagus nerve are retracted laterally and exposure of the subclavian artery and its

proximal branches proceeds after division of vertebral vein

g. Divide anterior scalene muscle at its attachment on the first rib – care is taken to identify and protect phrenic nerve

h. Thyrocervical trunk can be divided for further mobilization of the subclavian artery.

Video: http://www.surgicalcore.org/videoplayer/510000063/58

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