Thorax

Intercostal Spaces

Intercostal spaces

• Separate the ribs and their costal cartilages from one another.

• The spaces are named according to the rib forming the superior border of the space(4th intercostal space lies between rib 4 and rib 5).

• Space below the 12th rib does not lie between ribs and thus is referred to as the subcostal space.

Contents of Intercostal Spaces

• 1. Intercostal Muscles: External intercostal, the internal intercostal, and the innermost intercostal muscle

• 2. The intercostal nerves and blood vessels run between the intermediate and deepest layers of muscles.

• They are arranged in the following order from above downward: intercostal vein, intercostal artery, and intercostal nerve (i.e., VAN).

Muscles of the Thoracic Wall

• The intercostal muscles are arranged as three layers (external layer, internal layer and an

incomplete innermost layer) between the ribs. The three layers of the intercostal muscles are:

• External layer -- External intercostal • Internal layer -- Internal intercostal • Innermost layer -- Transversus thoracic (anterior),

Innermost (lateral) and subcostal (posterior)

A simple model of the action of the intercostal muscles

Vasculature of the Thoracic Wall

Arteries of the Thoracic Wall

• The arterial supply to the thoracic wall derives from the:

• 1. Thoracic aorta, through the posterior intercostal and subcostal arteries.

• 2. Subclavian artery, through the internal thoracic and supreme intercostal arteries.

The posterior intercostal arteries:

• Of the 1st and 2nd intercostal spaces arise from the supreme (superior) intercostal artery, a branch of the costocervical trunk of the subclavian artery.

• Of the 3rd to 11th intercostal spaces (and the subcostal arteries of the subcostal space) arise posteriorly from the thoracic aorta.

Anterior intercostal arteries:

• Supply the anterior parts of the upper 9 intercostal spaces.

• Of the 7 to 9th intercostal spaces derive from the musculophrenic arteries, also branches of the internal thoracic arteries.

• Are absent from the inferior two intercostal spaces; these spaces are supplied only by the posterior intercostal arteries and their collateral branches.

Notching of the ribs

• Coarctation of the aorta: The word “coarctation” means narrowing. 

• Congenital condition whereby the aorta narrows in the area where the ductus arteriosus (ligamentum arteriosum after regression) inserts.

• It is associated with notching of the ribs

 (because of collateral circulation)

Notching of the ribs

Veins of the Thoracic Wall

• There are 11 posterior intercostal veins and one subcostal vein on each side.

• Most posterior intercostal veins (4 to11) end in the azygos/hemiazygos venous system, which conveys venous blood to the SVC.

Nerve Supply

• The intercostal muscles are supplied by the corresponding intercostal nerves.

• The intercostal nerves are the anterior rami of the first 11 thoracic spinal nerves.

• The anterior ramus of the 12th thoracic nerve lies in the abdomen and runs forward in the abdominal wall as the subcostal nerve.

Branches

• 1. The lateral cutaneous branch reaches the skin on the side of the chest. It divides into an anterior and a posterior branch.

• 2. The anterior cutaneous branch, which is the terminal portion of the main trunk, reaches the skin near the midline. It divides into a medial and a lateral branch.

• 3. The collateral branch runs forward inferiorly to the main nerve on the upper border of the rib below.

Segmental innervation (dermatomes) of thoracic wall.

• Spinal nerve C5 supplies skin at the level of the clavicles .

• Anteriorly, the dermatome immediately inferior to the C5 dermatome is that of spinal nerve T1.

• Dermatomes C6 to C7 are located mostly in the upper limbs

• Dermatome T4 includes the nipple. Dermatome T10 includes the umbilicus.

Herpes Zoster Infection of the Spinal Ganglia

• A herpes zoster infection causes a classic, dermatomally distributed skin lesion shingles.

• Herpes zoster is primarily a viral disease of spinal ganglia(varicella-zoster virus (VZV), or chickenpox virus).

• After invading a ganglion, the virus produces a sharp burning pain in the dermatome supplied by the involved nerve.

Herpes Zoster Infection of the Spinal Ganglia

Intercostal Nerve Block

• This procedure, an intercostal nerve block, involves infiltration of the anesthetic around the intercostal nerve trunk and its collateral branches.

• Indications

• Intercostal nerve block is indicated for repair of lacerations of the thoracic and abdominal walls, for relief of pain in rib fractures, and to allow pain-free respiratory movements.

Procedure

Thoracic Outlet Syndrome

• Syndrome involving compression at the superior thoracic outlet.

•  It can affect the  Lower trunk of brachial plexus,subclavian artery or rarely the vein.

• Classification• 1.Cervical rib syndrome

• 2. Costoclavicular syndrome

Cervical rib

• A cervical rib is a supernumerary (or extra) rib which arises from the seventh cervical vertebra.

• Present in only about 1 in 500 (0.2%) of people.

• The presence of a cervical rib can cause a form of thoracic outlet syndrome due to compression of the lower trunk of the brachial plexus or subclavian artery.

Cervical rib