Serving as the link between the powerful movements of the shoulder and the fine motor control of the hand, the elbow is often overlooked as an area of potentially disabling injury. Even minor injuries to the elbow can severely hamper the ability to perform the most rudimentary movements. Fractures or other trauma involving the elbow or forearm can result in impairment of the neurovascular structures supplying the wrist, hand, and fingers. Additionally, pathology at the shoulder can influence movement patterns and stresses at the elbow. Therefore, examination of the elbow and forearm is often expanded to include the hand and shoulder.
The humerus, radius, and ulna form the elbow joint. The radius and ulna continue on to form the proximal and distal radioulnar joints of the forearm. The distal end of the humerus flares to form the medial and lateral epicondyles, with the medial epicondyle larger than the lateral. Between the epicondyles lie the capitulum and the trochlea, the articulating surfaces for the radius and ulna. Separated from the trochlea by the trochlear groove, the capitulum forms the lateral humeral articulating surface on the distal border of the lateral epicondyle. Unlike the trochlea, the domeshaped capitulum does not extend to the posterior aspect of the humerus. Located immediately above the capitulum, the radial fossa is an indentation in the lateral epicondyle that accepts the radial head during elbow flexion (Fig. 16-1). The distal end of the humerus is anteriorly rotated 30 degrees relative to the humeral shaft.
Bony anatomy of the distal humerus. The trochlea articulates with the ulna; the capitulum, with the radial head.
The ulna forms the medial border of the forearm. Proximally, the ulna articulates with the humerus and radius. The proximal border of the ulna is formed by the olecranon process, a projection that fits into the humeral olecranon fossa during complete extension of the elbow.
The semilunar notch, an indentation lined with articular cartilage, fits snugly around the humeral trochlea. The distal border of the semilunar notch is formed by the coronoid process. The ulnar coronoid process is received by the coronoid fossa of the humerus during elbow flexion. Lateral and slightly distal to the coronoid process, the radial notch is an indentation that accepts the radial head to form the proximal radioulnar joint (Fig. 16-2).
Bony anatomy of the radius and ulna.
Located on the thumb-side of the forearm, the radius is lateral to the ulna when the body is in its anatomical position. The proximal articulating surface, the radial head, is disk shaped and concave to allow gliding and rotation on the capitulum, significantly ...