Imaging of the elbow includes assessment of the three-joint complex: humeroulnar, humeroradial, and proximal radioulnar. The function of these three joints is to allow the hand to be positioned to enable the desired actions to be accomplished. The distal humerus provides medial (trochlea—articulates with ulna) and lateral (capitulum or capitellum—articulates with radius) articular areas of their respective condyles (Figure 6–1). Three concavities (fossae) are present, two anteriorly—coronoid (accepts/articulates with ulna in flexion) and radial (accepts/articulates with radius in flexion), while there is one posteriorly—olecranon (accepts/articulates with the olecranon process of the ulna in extension). The most proximal radius is composed of the head, which includes a cup-like superior projection to articulate with the capitulum, while the circumferential surface articulates with the radial notch of the ulna. The remaining proximal radius is composed of the bicipital tuberosity and the neck. The medial and lateral epicondyles of the humerus serve as insertional sites for ligaments and tendons.
Diagram of bony features of the elbow.
The minimal screening series for the elbow includes the anteroposterior (AP) and lateral projections. In some facilities, the additional oblique view is a part of protocol. Most of the time, elbow films are performed after trauma, and thus the focus is on fracture recognition, and often the forearm is also a part of the assessment related to the interrelatedness of these functional units (Greathouse, 1998).
The AP view is taken with the patient seated and the elbow extended, externally rotated, and with the normal carrying angle (typically 10 to 15 degrees) of the individual. The film exhibits the distal humerus, proximal radius, proximal ulna, and their respective articulations (Figure 6–2). The general anatomy is relatively well defined with some superimposition of a portion of the radial head and proximal radius with ulna with the olecranon process of the ulna well seated on the trochlea and into the olecranon fossa, again superimposed through the humerus.
A radiograph demonstrating a normal-appearing elbow in an AP view.
The lateral view is accomplished with the patient seated and the elbow flexed to 90 degrees and the thumb up (neutral forearm position). This view best outlines the olecranon and the anterior radial head in profile. It also can exhibit supracondylar humerus fractures, particularly through the fat pad sign—soft tissue projections (fat pad) out of their normal fossa locations (Figure 6–3).
A lateral view radiograph of a normal-appearing elbow.
Oblique views are sometimes added if concern is focused on the coronoid process (internal oblique rotation view) or the proximal radius/head (external oblique rotation view). These structures are ...