Boundaries
The cubital fossa is a triangle with its base above and its apex pointing distally. Each side is formed by a muscle arising from one epicondyle of the humerus.
- Superior (base): an imaginary line joining the medial and lateral epicondyles of the humerus.
- Lateral: the medial border of brachioradialis.
- Medial: the lateral border of pronator teres.
- Apex: the point where brachioradialis and pronator teres meet distally.
The roof is skin, superficial fascia and deep fascia. The deep fascia is reinforced by the bicipital aponeurosis, a flat band that runs from the biceps tendon medially into the deep fascia over the forearm flexors. The floor is brachialis in its upper part and supinator in its lower part.
Contents
The contents of the cubital fossa, from lateral to medial, are the radial nerve, the tendon of biceps brachii, the brachial artery and the median nerve.
| Structure | Position | What happens to it |
|---|---|---|
| Radial nerve | Most lateral, tucked under brachioradialis on brachialis | Divides into the superficial branch (sensory) and the deep branch, which enters supinator as the posterior interosseous nerve |
| Biceps tendon | Centre of the fossa | Passes deeply to insert on the radial tuberosity; gives off the bicipital aponeurosis medially |
| Brachial artery | Medial to the tendon, under the aponeurosis | Divides into the radial and ulnar arteries, usually at the level of the neck of the radius |
| Median nerve | Most medial | Leaves the fossa between the two heads of pronator teres |
The ulnar nerve is not a content of the fossa. It passes behind the medial epicondyle, in the cubital tunnel, and enters the forearm between the heads of flexor carpi ulnaris. Small lymph nodes and the deep veins accompanying the artery (venae comitantes) also lie in the fossa.
Relations: the roof and superficial veins
The superficial veins of the roof lie outside the deep fascia and are separated from the brachial artery by the bicipital aponeurosis. The cephalic vein runs up the lateral side and the basilic vein up the medial side. The median cubital vein links them, running obliquely upwards and medially from cephalic to basilic across the aponeurosis. The pattern varies between people, and some have a median forearm vein that splits into two.
Two cutaneous nerves run in the roof beside the veins. The lateral cutaneous nerve of the forearm, the terminal branch of the musculocutaneous nerve, emerges lateral to the biceps tendon. The medial cutaneous nerve of the forearm runs with the basilic vein.
Clinical relevance
The cubital fossa is where clinicians take blood, measure blood pressure and meet the neurovascular complications of elbow fractures.
- Venepuncture: the median cubital vein is large, fixed and superficial. The bicipital aponeurosis lies between it and the brachial artery, which protects the artery from a needle passed too deeply.
- Blood pressure: the stethoscope goes over the brachial artery just medial to the biceps tendon, where the pulse is palpable.
- Supracondylar fracture of the humerus: common in children after a fall on the outstretched hand. The displaced proximal fragment can injure the brachial artery and the median nerve, particularly its anterior interosseous branch. Untreated ischaemia of the forearm flexors leads to Volkmann's ischaemic contracture.
- Inadvertent intra-arterial injection: an anomalous high division of the brachial artery can place an artery superficially in the roof.
- Distal biceps tendon rupture: the tendon can no longer be felt in the fossa, and supination is weak.