The cubital fossa is a triangular shaped area or depression situated in relation to the ventral surface of the forearm and contains important neurovascular structures. It has a superior, medial and lateral border, as well as an apex which is directed inferiorly. The cubital fossa also has a floor and roof, and it is traversed by structures which makes up its contents.
The superior border – also known as the base – of the cubital fossa, is formed by an imaginary line that runs from the medial epicondyle of the humerus (bone of arm) to the lateral epicondyle of the humerus.
This border of the triangle is formed by the pronator teres muscle.
The triangle is formed at this boundary by the brachioradialis muscle.
The apex is directed inferiorly, and it is formed by the pronator teres and brachioradialis muscles, at the point where these two muscles meet and cross over each other.
This is formed, from superficial to deep, by the skin, fascia of the forearm and the bicipital aponeurosis (medially). The bicipital aponeurosis forms a partial protective covering to the medial nerve, brachial artery, radial artery and ulnar artery.
The cubital fossa contains four structures, which from medial to lateral are:
- the median nerve
- the brachial artery
- the tendon of biceps brachii (biceps brachii is a muscle of the anterior compartment of the arm)
- the radial nerve
Within the cubital fossa, the brachial artery bifurcates to form two more arteries. These arteries are the radial artery (laterally) and the ulnar artery (medially). These two arteries are named and situated in accordance with the radial and ulnar bones of the forearm.
The fascia forming the roof also contains the median cubital vein, the lateral cutaneous nerve of the forearm, and medial cutaneous nerve of the forearm. On the bicipital aponeurosis lies the basilic vein (medially) and the cephalic vein (laterally).
The cubital fossa is a common site for sampling and transfusion of blood, and intravenous injections because of the prominence and accessibility of the 'attending' veins. The median cubital vein is most commonly accessed for venipuncture. A tourniquet is placed around the midarm to distend the veins in the cubital fossa. Once the vein is punctured, the tourniquet is removed so that when the needle is removed, the vein will not bleed extensively. The median cubital vein is also a site for the introduction of cardiac catheters to secure blood samples from the great vessels and chambers of the heart. This route may also be used for coronary angiography.
Blood Pressure Measurements
The cubital fossa is a site for placement of the diaphragm of the stethoscope during blood pressure measurement to palpate the pulse of the brachial artery.