Post on 03-Jan-2016
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)
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)
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.
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.
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.