Radiographic Anatomy of Elbow

Radiographic Anatomy of Elbow:

Elbow Joint: It is also a freely movable or diarthrodial synovial joint. It is generally considered a ginglymus (hinge) type of joint. In addition to the hinge joints between the humerus and ulna and the humerus and radius, the proximal radioulnar joint (trochoidal or pivot-joint) also is considered part of the elbow joint.

Radial head: The head of radius participates in two joints, the elbow and the superior radio-ulnar joint.

Lower end of humerus: It presents lateral epicondyle, capitulum, trochlea, and the medial epicondyle from lateral to medial side.

Fat pads: Three fat pads are present: in the radial fossa, in the coronoid fossa and in the olecranon fossa.

Upper end of ulna: It presents two processes: the olecranon and the coronoid processes. The olecranon and the coronoid processes having concavity presenting anteriorly. Articular surface of the coronoid process is like a seat of the chair while the articular surface of the olecranon is like the back rest of the chair.

Upper end of radius: It presents radial head having an articular facet on the top which articulates with the capitulum.

Capitulum: It articulates with the head of radius and the trochlea with the trochlear notch of the ulna. Above the capitulum, lies the radial fossa and the trochlear fossa is above the coronoid. The posterior aspect of the lower end of humerus presents the olecranon fossa. The head of radius presents a shallow articular depression for capitulum. The trochlear notch is formed by coronoid and olecranon processes.

Humerus: It is the long bone of the arm having the shaft, upper and the lower ends. It takes part in the formation of shoulder joint at the upper end and the elbow joint at the lower end.

Upper end of humerus: It consists of hemi-spherical head, covered with the articular cartilage, greater tubercle and the lesser tubercle. Head of humerus is directed backwards, upwards and medially. The head articulates with the glenoid cavity of the scapula and forms the shoulder joint. Area beyond the articular surface of the head is known as anatomical neck.

Lesser tubercle: It is situated in front of the upper end and forms the medial limit of the groove known as intertubercular groove or sulcus. This gives insertion to the subscapularis muscle.

Greater tubercle: It is the lateral prominence at the upper end. It forms the lateral boundary of the intertubercular groove. It presents three impression starting from the top to the back. They are for supraspinatus, infraspinatus and teres minor.

Surgical neck: It is at the upper end of the shaft of humerus below the anatomical neck.

Clavicle: It is a long bone placed horizontally in the body. It presents shaft, which is like letter “f”, two ends, acromial or lateral and sternal or medial. It articulates laterally with acromion to form acromio-clavicular joint and medially with manubrium sterni to form sternoclavicular joint.lz

Scapula: It is the flat triangular bone placed at the postero-lateral aspect of the chestwall. It has three borders, three processes, three angles and three fossae..

Infraglenoid tubercle: It is the rough triangular area situated below glenoid cavity.

Supraglenoid tubercle: It is above the glenoid cavity.

Glenoid cavity: It is a shallow, pear-shaped cavity at the lateral angle of the scapula, narrow above and broad below. It takes part in the formation of the shoulder joint with the head of humerus, which is larger in size of the glenoid cavity.

Coracoid process: It is a thick stout process above the supraglenoid tubercle like a bent thumb.

Neck of scapula: This is the part adjoining the glenoid cavity.

Supraspinatus fossa: It lies above the spine and infraspinatus fossa below. These two fossae communicate with each other through the spino-glenoid notch.

Acromion: It articulates with the lateral end of clavicle to form the acromioclavicular joint.

Fig: Lateral view of Elbow showing lines

Anterior humeral line: On a normal lateral radiograph, it is a line traced along the anterior cortex of the humerus will bisect the capitellum between its anterior and middle thirds. If less than one third of the capitellum lies anterior to the line then there may be a supracondylar fracture with posterior displacement of the distal fragment.

Radio-capitellar line: It is a line drawn along the center of the shaft of the proximal radius passing through the capitellum. If the line does not pass through the capitellum then either the radial head or the capitellum is displaced.

Mid-humeral line: It is a line coincident with the central axis of the humeral shaft, projects just posterior to the posterior margin of the capitulum.

Fig: Elbow AP and Lateral views