Superficial structures and venous anastomoses
Major venous trunks are located in the deep layer of the subcutaneous tissue of the cubital fossa. On the medial side runs the basilic vein (v. basilica) accompanied by branches of the medial antebrachial cutaneous nerve. On the lateral side lies the cephalic vein (v. cephalica) alongside the lateral antebrachial cutaneous nerve.
Superficial veins anastomose with each other, forming two typical patterns:
- N-shaped (H-shaped) type: the classic variant where v. basilica and v. cephalica are connected by the obliquely running median cubital vein — v. mediana cubiti.
- M-shaped type: the median vein of the forearm divides into two branches — v. mediana cephalica and v. mediana basilica, which drain into the respective main veins.
Regardless of the structural type, the superficial veins of the cubital fossa are connected to the deep veins via a perforating branch. This anchors them to the deep fascia, preventing them from "slipping away" during intravenous injections.
Deep fascia and muscle compartments
The deep fascia (fascia propria) over the medial muscle group appears as a dense aponeurosis. It is additionally reinforced by fibers of the bicipital aponeurosis (aponeurosis bicipitalis). The medial and lateral intermuscular septa extend inward from the fascia, forming three fascial compartments:
- Medial compartment: contains muscles originating from the medial epicondyle. The superficial layer (from the elbow inward) is formed by the flexor carpi ulnaris, palmaris longus, flexor carpi radialis, and pronator teres. The flexor digitorum superficialis lies in the deep layer.
- Middle compartment: the biceps brachii muscle (m. biceps brachii) lies superficially, while deeper lies the brachialis muscle (m. brachialis), covering the joint capsule.
- Lateral compartment: includes the brachioradialis muscle (m. brachioradialis) and the supinator underlying it.
Deep vessels and nerves
The main neurovascular bundle runs along the medial edge of the biceps tendon, located within the splitting of the medial septum on the brachialis muscle. The brachial artery (a. brachialis) runs accompanied by veins, and the median nerve (n. medianus) is located 0.5–1.0 cm medially from it.
1–2 cm below the epicondylar line (under the bicipital aponeurosis), the brachial artery divides into two main branches:
- Radial artery (a. radialis): crosses the biceps tendon anteriorly, passing laterally into the gap between the pronator teres and brachioradialis muscles.
- Ulnar artery (a. ulnaris): dives under the pronator teres, positioned between the superficial and deep finger flexors.
Topography of the elbow joint
The fibrous capsule of the elbow joint has a specific attachment line. On the humerus, it attaches above the coronoid, radial, and olecranon fossae, leaving both epicondyles outside the joint cavity. On the radius, the capsule is fixed to the neck, where the synovial membrane forms a downward-directed sacciform recess (recessus sacciformis).
Syntopy (muscular protection) of the capsule:
- Anteriorly: almost entirely covered by the brachialis muscle.
- Externally: protected by the supinator.
- Posteriorly: covered by the triceps tendon and anconeus muscle.
- Medially: muscles are absent; the capsule is covered only by fascia and skin.
A synovial bursa (bursa subcutanea olecrani) is located in the subcutaneous tissue over the apex of the olecranon process. Trauma or constant pressure (occupational hazards of watchmakers, engravers) can lead to inflammation in it, known as bursitis.
The order of the superficial muscles of the medial compartment (from the medial edge inward) can be memorized by the initials: flexor carpi ulnaris, palmaris longus, flexor carpi radialis, pronator teres.
Class and exam questions
Why is the median cubital vein (v. mediana cubiti) preferred for venipuncture?
It is relatively immobile due to anastomosis with deep veins (fixed to the fascia) and lacks large superficial cutaneous nerves nearby, which reduces the risk of nerve injury during injection.
Where is the level of bifurcation of the brachial artery?
The brachial artery divides into the radial and ulnar arteries 1–2 centimeters below the line connecting the humeral epicondyles, beneath the bicipital aponeurosis.
How do the compartments of the elbow joint cavity communicate?
The anterior and posterior compartments communicate only through narrow clefts along the radial and ulnar sides. During inflammation of the synovial membrane, these clefts may close, isolating the compartments from each other.
Which structures protect the capsule of the elbow joint from the medial side?
Medially, the joint capsule is not protected by muscles; it is covered exclusively by the deep fascia and skin.
What else to study on this topic
- Formation of the elbow arterial network and anastomoses
- Topography of the ulnar and radial nerves in the cubital region
- Structure and functions of the bicipital aponeurosis
- Topography of the posterior cubital region and synovial bursa
- Features of the joint synovial membrane and fat pads
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