The Cubital Fossa
The cubital fossa is an area of transition between the anatomical arm and the forearm. It is located as a depression on the anterior surface of the elbow joint.
In this article, we shall look at the borders and contents of the cubital fossa, including any clinical relevance.
The cubital fossa is triangular in shape, and thus has three borders:
- Lateral border – medial border of the brachioradialis muscle.
- Medial border – lateral border of the pronator teres muscle.
- Superior border – hypothetical line between the epicondyles of the humerus.
The floor of the cubital fossa is formed proximally by the brachialis, and distally by the supinator muscle. The roof consists of skin and fascia, and is reinforced by the bicipital aponeurosis. Within the roof runs the median cubital vein, which can be accessed for venepuncture (see clinical relevance below).
The contents of the cubital fossa include vessels, nerves and the biceps tendon (lateral to medial):
- Radial nerve – This is not always strictly considered part of the cubital fossa, but is in the vicinity, passing underneath the brachioradialis muscle. As is does so, the radial nerve divides into its deep and superficial branches.
- Biceps tendon – It runs through the cubital fossa, attaching to the radial tuberosity, just distal to the neck of the radius.
- Brachial artery – The brachial artery supplies oxygenated blood the forearm. It bifurcates into the radial and ulnar arteries at the apex of the cubital fossa.
- Median nerve – Leaves the cubital between the two heads of the pronator teres. It supplies the majority of the flexor muscles in the forearm.
Mnemonic for contents of the cubital fossa – Really Need Beer To Be At My Nicest.
Brachial Pulse and Blood Pressure
The brachial pulse can be felt by palpating immediately medial to the biceps tendon in the cubital fossa. When measuring blood pressure, this is also the location in which the stethoscope must be placed, to hear the korotkoff sounds.
The median cubital vein is located superficially within the roof of the cubital fossa. It connects the basilic and cephalic veins, and can be accessed easily – this makes it a common site for venepuncture.
A supracondylar fracture is a common fracture in the young, and usually occurs by falling onto a hyper-extended elbow. It is a transverse fracture, spanning between the two epicondyles. It can also occur by falling onto a flexed elbow, but this accounts for <5% of cases.
The displaced fracture fragments may impinge and damage the contents of the cubital fossa.
Direct damage, or post-fracture swelling can cause interference to the blood supply of the forearm from the brachial artery. The resulting ischaemia can cause Volkmann’s ischaemic contracture – uncontrolled flexion of the hand, as flexors muscles become fibrotic and short.
There also can be damage to the median or radial nerves.