The intercostal space
Typically, each space contains three muscles comparable to those of the abdominal wall. These include the:
• External intercostal: this muscle fills the intercostal space from the vertebra posteriorly to the costochondral junction anteriorly where it becomes the thin anterior intercostal membrane. The fibres run downwards and forwards from rib above to rib below.
• Internal intercostal: this muscle fills the intercostal space from the sternum anteriorly to the angles of the ribs posteriorly where it becomes the posterior intercostal membrane which reaches as far back as the vertebral bodies. The fibres run downwards and backwards.
• Innermost intercostals: this group comprises the subcostal muscles posteriorly, the intercostales intimi laterally and the transversus thoracis anteriorly. The fibres of these muscles span more than one intercostal space.
The neurovascular space is the plane in which the neurovascular bundle (intercostal vein, artery and nerve) courses. It lies between the internal intercostal and innermost intercostal muscle layers. The intercostal structures course under cover of the subcostal groove. Pleural aspiration should be performed close to the upper border of a rib to minimize the risk of injury.
Structures in intercostal space
- several kinds of intercostal muscle
- intercostal arteries and associated veins