External and topographical landmarks
Upon inspection and palpation of the posterior elbow region, three main external bony landmarks are distinguished, allowing the surgeon to accurately determine the projection of internal structures:
- Medial epicondyle of the humerus — a prominent bony prominence on the inner side of the joint.
- Lateral epicondyle of the humerus — a landmark on the outer side serving as the origin site for the extensor muscles of the wrist and fingers.
- Olecranon of the ulna (olecranon) — the most massive and posteriorly prominent bony structure.
Directly on both sides of the massive olecranon, two important topographical depressions are formed. On the inner side lies the posterior medial ulnar sulcus (sulcus cubitalis posterior medialis), and on the outer side — the posterior lateral ulnar sulcus (sulcus cubitalis posterior lateralis). These grooves serve as essential guides when searching for neurovascular bundles.
Fascial and muscular apparatus of the region
The soft tissue anatomy of the posterior elbow is characterized by high strength of connective tissue structures. The deep fascia here is characterized as very dense. It is additionally reinforced by bundles of fibrous fibers extending from the tendon of the triceps brachii muscle (m. triceps brachii). An important topographical feature of the deep fascia is that it tightly fuses with the epicondyles of the humerus and the posterior border of the ulna, forming isolated spaces.
Beneath the deep fascia lies the muscle layer, represented mainly by the distal parts of the triceps brachii muscle:
- In the upper half of the medial part of the region runs the medial head of the m. triceps brachii, which gradually passes into a powerful tendon.
- On the lateral side lies the lateral head of the same muscle, also participating in the formation of the common tendon.
Ultimately, the combined tendon of the triceps brachii firmly attaches to the olecranon (olecranon). To reduce friction beneath the tendon at its attachment site to the bone, a special synovial bursa is located — bursa subtendinea m. tricipitis brachii. In turn, the lateral epicondyle acts as a fixation point from which the extensor muscles of the wrist and fingers originate.
Topography and clinical significance of the ulnar nerve
The ulnar nerve (n. ulnaris) is a key structure of the posterior elbow region. Along its course, it is accompanied by the superior ulnar collateral artery (a. collateralis ulnaris superior).
Course of the nerve in the elbow region:
- Initially, the ulnar nerve emerges from the thickness of the medial head of the triceps brachii muscle.
- Descending to the level of the epicondyles, the nerve lies in the posterior medial ulnar sulcus (sulcus cubitalis posterior medialis).
- In this zone, the nerve passes inside a specialized osteofibrous canal. This canal is formed by three structures: the medial epicondyle, the olecranon, and the dense deep fascia stretched between them.
- The most important anatomical feature of this section is that the ulnar nerve here lies closely adjacent to the capsule of the elbow joint.
- At the lower boundary of the described region, the nerve goes under the forearm muscles — the flexor carpi ulnaris (m. flexor carpi ulnaris) and the flexor digitorum superficialis (m. flexor digitorum superficialis), heading further into the anterior compartment of the forearm.
Clinical significance: Due to the fact that the ulnar nerve in the osteofibrous canal is located extremely superficially and lies directly next to dense bone tissue, it is very often subjected to mechanical trauma. When this area is struck or compressed, a characteristic symptom occurs — sharp, brief burning pain. In more severe cases, trauma can lead to complete or partial loss of motor and sensory function of the nerve.
To memorize the walls of the ulnar nerve canal, use the triad: "Bone, Bone, and Fascia" — medial epicondyle (bone), olecranon (bone), and deep fascia (roof).
Class and exam questions
It runs in the posterior medial ulnar sulcus (sulcus cubitalis posterior medialis), inside the osteofibrous canal between the medial epicondyle and the olecranon.
It runs in the posterior medial ulnar sulcus, forming an osteofibrous canal between the medial epicondyle, the olecranon, and the deep fascia.
Why does elbow trauma often cause burning pain?
This is due to the superficial location of the ulnar nerve. In the posterior medial sulcus, it lies immediately beneath the skin and fascia, adjacent to the bone, which is why it is easily injured upon impact.
Which structure protects the triceps tendon from friction?
Beneath the tendon of the triceps brachii muscle at its attachment site to the olecranon is a synovial bursa — bursa subtendinea m. tricipitis brachii.
Where does the ulnar nerve go from the posterior elbow region?
At the lower boundary of the region, it heads into the anterior compartment of the forearm, passing beneath the flexor carpi ulnaris and flexor digitorum superficialis.
What else to study on this topic
- Detailed anatomy of the synovial bursa of the triceps muscle (bursa subtendinea m. tricipitis brachii).
- The relationship of the ulnar nerve with the capsule of the elbow joint in the osteofibrous canal.
- Origin points of the wrist and finger extensor muscles on the lateral epicondyle.
- Anatomical prerequisites for compression neuropathies of the ulnar nerve.
- The mechanism of reinforcement of the deep fascia by fibrous fibers of the triceps tendon.
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