Anatomy - Anterolateral thoracotomy

Beneath the skin of the thorax, there are several fasciae and muscle layers from the outside inwards: The pectoral fascia is a fascia that lies externally on the pectoralis major muscle, while the clavipectoral fascia envelops the pectoralis minor muscle. The bony thorax itself also has its own fasciae: The thoracic fascia covers the periosteum of the ribs and the muscles of the intercostal spaces from the outside, while the endothoracic fascia represents its inner counterpart on the periosteum of the ribs and the inner or innermost intercostal muscles. It is covered by the parietal pleura (pleural membrane) in relation to the interpleural space. All these fasciae, including the intercostal musculature (see below), are penetrated during thoracotomy.

Blood vessels (intercostal vessels) and nerves (intercostal nerves) of the thoracic wall run in a ring-like manner along the inner side of the thorax, corresponding to the original segments of the organism. The blood vessels segmentally connect the dorsally located vessels aorta and V. azygos/hemiazygos with the respective ventral A. and V. thoracica interna. This arises from the A. subclavia, runs together with the eponymous accompanying veins bilaterally parallel to the sternum immediately outside the fascia endothoracica caudally, and then divides at the diaphragm level (Larrey's slit) into the A. epigastrica sup. (anastomoses with the A. epigastrica inf. from the A. iliaca externa) and an artery to the diaphragm (A. musculophrenica). Along this path, on the inner side of the thorax, it primarily gives rise to the anterior parts of the intercostal arteries and branches to the mediastinum.

The intercostal arteries thus have an anterior inflow from the internal thoracic artery and are supplied dorsally either directly from the aorta (3rd – 11th branch) or the subclavian artery (via the costocervical trunk). Below the 12th rib, the subcostal artery runs as a counterpart. Regarding the overall course of the intercostal arteries, it is important to note that the dorsal portions of the arteries run along the lower edge of the overlying rib (together with the intercostal vein and nerve) up to the level of the anterior axillary line and then typically divide into an upper and a lower branch (at the lower and upper edge of the adjacent ribs). Typical clusters of lymph nodes are found in the area of the chest wall parasternal, axillary, and just above and below the clavicle.