The Cubital Fossa is an area of transition between the anatomical arm and the forearm. It is located in a depression on the anterior surface of the elbow joint. It is also called the antecubital fossa because it lies anteriorly to the elbow (Latin cubitus) when in standard anatomical position. The cubital fossa is triangular, and thus has three borders along with an apex which is directed inferiorly. It also has a floor and roof, and it is traversed by structures that make up its contents.[rx][rx][rx][rx]
Borders
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Lateral border – is the medial border of the brachioradialis muscle.
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Medial border – is the lateral border of the pronator teres muscle.
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Superior border – is an imaginary 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 which is a sheet of tendon-like material that arises from the tendon of the biceps brachii. The bicipital aponeurosis forms a partial protective covering to the medial nerve, brachial artery and ulnar artery. Within the roof runs the median cubital vein, which can be accessed for venipuncture (see clinical significance below).
Structure of Cubital Fossa
The cubital fossa contains four main vertical structures from lateral to medial.[rx][rx][rx][rx]
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The radial nerve – 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.
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Biceps tendon – Iruns through the cubital fossa, attaching to the radial tuberosity, just distal to the neck of the radius.
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Brachial artery supplies – oxygenated blood the forearm. It bifurcates into the radial and ulnar arteries at the apex of the cubital fossa.
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Median nerve – leaves the cubital between the two heads of the pronator teres. It supplies the majority of the flexor muscles in the forearm.
Blood Supply of Cubital Fossa
As stated above, the brachial artery passes through the cubital fossa, bifurcating into the radial and ulnar arteries at the distal apex of the fossa. These arteries then continue down into the forearm to supply the anterior and posterior aspects of the lower arm, ending with the deep and superficial arches of the hand.
The two primary superficial veins of the arm have an essential communication in the roof of the cubital fossa – the median cubital vein. The cephalic vein commences on the anterolateral surface of the wrist, and the basilic vein begins on the anteromedial aspect of the wrist. They continue up the forearm into the arm, connecting with the median cubital vein on the way. The basilic vein joins with the brachial vein to form the axillary vein (at the lower border of teres major), with the cephalic vein then draining into the axillary vein within the axilla region.[rx]
Nerves Supply of Cubital Fossa
As mentioned above, two of the primary nerves of the arm run through the cubital fossa – the median and radial nerves.
The median nerve, with C6-T1 roots, innervates the majority of the muscles of the anterior forearm (barring the ulna nerve innervated flexor carpi ulnaris and ulnar half of flexor digitorum profundus), the muscles of the thenar eminence of the hand, and the medial two lumbricals. As such, it plays a vital role in flexion of the wrist, pronation of the forearm, and movements of the fingers. It supplies sensory innervation to the lateral palm and volar surface of the lateral three and one-half digits.
The radial nerve, with C5-T1 roots, innervates all of the muscles in the posterior compartment of the forearm, thus having a key role in wrist extension and movements of the fingers. It supplies sensory innervation to the lateral aspect of the dorsum of the hand and dorsal surface of the lateral three and one-half digits.[rx]
Physiologic Variants
Research has reported variations in the anatomy of the structures of the cubital fossa:
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Radial nerve – the main variations occur at its site of bifurcation. As described above, this most commonly occurs within the cubital fossa but may occur proximal or distal to the fossa.[rx]
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Biceps tendon – the distal tendon may appear bifurcated if there has been continuing the separation of the short and long heads.[rx]
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Brachial artery – similarly to the radial nerve, the main variations occur relative to its bifurcation. While most commonly occurring at the apex of the cubital fossa, this can occur more distally down the arm. There have even been reports of an absent brachial artery, with the ulnar and radial arteries coming directly from the axillary artery.[rx]
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Median nerve – the anatomy is relatively constant at the cubital fossa, with the majority of variations occurring further down the arm at the level of the carpal tunnel.[rx]
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Median cubital vein – there are several variations of the vein, with previous criteria developed as[rx]:
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A dominant median antebrachial vein of the forearm joining the basilic and cephalic veins in the fossa
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The median cubital vein connecting the basilic and cephalic veins (the most common, and as described above)
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Median cubital vein present, but absent development of the cephalic artery in the upper arm
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No communication present between the cephalic and basilic veins
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Anatomically the superficial veins of the cubital fossa are classified into four types according to the presence of the median cubital vein (MCV) or median antebrachial vein.
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Type I: The median antebrachial vein is dominant and joins both cephalic vein (CV) and basilic vein (BV) in the cubital region. This is also called N type.
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Type II: The median cubital vein connects both cephalic vein and basilic vein in the cubital region. This type is also called type M type.
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Type III: In the cubital region, development of the brachial cephalic vein is poor or missing.
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Type IV: No communicating branch between the cephalic vein and basilic vein.
Type II presenting the both cephalic and basilic vein connected by the median cubital vein is most common followed by type I. Although the most common type of male and female was different as type I and type II, respectively, there is no statistical difference between them. The frequency of the types between right and left upper limbs was also not different. Because of the wide variations of these superficial veins, it has been reported that adverse effects such as bruising, hematoma, and sensory change occurred by mispuncture in various health care systems. Most medical practitioners are aware of two patterns of venous returns in the cubital fossa. This variation underlines the importance of using the intravenous illuminator for venipuncture.
References