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Ellenbogen Anatomie für Ultraschall

ANATOMY FACTS FOR ULTRASOUND

ELBOW JOINT CAPSULE (EC) has two layers: The joint capsule and the common extensor tendon blended with each other imperceptibly and formed a single enthesis at the lateral epicondyle. EC attaches proximally to the radial, coronoid and olecranon fossae. EC inserts into the annular ligament of the radius and the coronoid process of the ulna.

The radiocapitellar synovial fold is a triangular shaped thickening of the capsule located at the proximal edge of the annular ligament. The synovial fold could be injured by chronic repeated trauma related to pronation and supination. A hypertrophic synovial radiohumeral plica with lateral sided snapping elbow can be the reason for pain at the lateral elbow.

The volume of of the joint capsule is 24-30 ml.

THE FUNCTION OF THE CAPSULE OF THE ELBOW JOINT

The elbow passive extension is limited by the anterior capsule the anterior bundle of the MCL and the olecranon process. Olecranon fossa fat pad provide 5% of addiBonal extension (Walker 1977).

The elbow passive flexion is limited by the capsule, triceps, coronoid process and the radial head.

The resistance to varus stress in flexion and extension is mostly provide by the joint and the anterior capsule with the lateral collateral ligament (LCL) contribuBng< 10%.

THE FAT PAD (FP)

Elbow fat pads consists of three masses in radial, coronoid and olecranon fossae.

Fat pad location :intracapsular and extrasynovial . The anterior FP is an aggregate of the radial and coronal FP. It is parallel to the anterior distal humerus and superficially

limited by the brachialis muscle. The posterior FP is located into the deep olecranon fossa bordered anteriorly by the triceps tendon and the anconeus muscle.

Distension of an intact joint capsule displaces the FP The anterior FP is displaced anteriorly and superiorly The posterior FP is displaced posteriorly and superiorly.

ELBOW JOINT CARTILAGE

The Joint Cartilage: The greater sigmoid notch of the ulna does not have continuous cartilage. 90% of individuals have fatty or fibrous zissue (Walker 1977). 80% of the radial head is covered by hyaline cartilage. The anterolateral part lacks of cartilage.

THE ELBOW DYNAMIC STABILIZERS

Medial and lateral collateral ligaments.

Articular capsule.

Forearm flexor and extensor muscles.

The medial collateral ligament (MCL) consists on anterior, posterior and transverse bundles. The medial compartment of the elbow (the flexor muscles, the medial capsule and the medial ligaments) >> stronger stabilizer than the lateral compartment of the elbow. The anterior bundle of the MCL is stressed in extension. It is the principal elbow stabilizer in valgus stress. The FDS origin joints with the MCL inserBon (coronoid process) and reinforces the MCL. The posterior band of the MCL tightens in flexion.

Anatomical and functional study of the medial collateral ligament complex of the elbow

THE LATERAL COLLATERAL LIGAMENT COMPLEX (LCL)

The LCL is made up by the radial collateral ligament, the annular ligament and the lateral ulnar collateral ligament (anatomical variants include accessory collateral ligament). The LCL is the primary restraint to posterolateral rotatory instability of the elbow and varus stress. Posterolateral rotatory instability is the posterior dislocation of the radial head when the elbow is exposed to an association of axial compression, supination and valgus stress.

Association between LCL insufficiency and failure of conservative treatments of lateral epicondyle pain.

The radial collateral ligament (lateral epicondyle anteriorly -annular ligament and fascia of the supinator muscle).

The annular ligament primary stabilizer of the proximal radio-ulnar joint (radial notch ulna-posterior margin of the notch.

The lateral ulnar collateral ligament (lateral epicondyle, conBnuaBon of the RCL passing superficial to the annular ligament – supinator crest of the ulna).

The RCL can be differentiated from the CET with knowledge of the RCL humeral footprint extent, which measured 8.9 mm in length and comprised 54% of the combined RCL and CET footprints. LUCL is better seen in cobra position.

THE ELBOW KINETICS. THE PRIMARY MUSCLES.

The primary flexor of the elbow is the brachialis (anterior aspect of the humerus-anterior aspect of the proximal ulna) followed by the brachioradialis, the biceps and the extensor carpi radialis.

The primary extensor of the elbow is the triceps (long head- infraglenoid tubercle, medial and lateral posterior aspect of the humerus; common tendon insertion onto the olecranon process.)

The primary supinator is the biceps brachii generating more torque when the forearm is pronated.

The primary pronator is the pronator quadratus (regardless of the forearm position)