Chapter 16: Elbow and Forearm Pathologies

INTRODUCTION

The elbow is a modified hinge joint that serves to connect the forearm to the upper arm through the articulation of three bones: the ulna, radius, and humerus. The elbow is most stable at the end ranges of extension and flexion. Many of the injuries that occur at the elbow involve repetitive stresses, such as swinging a golf club or tennis racquet and overhead throwing activities.

CLINICAL ANATOMY

The elbow is formed by the articulations of the humerus, radius, and ulna. The radius and ulna continue to form the forearm, including the proximal and distal radioulnar joints of the wrist.

Bony Anatomy

The distal end of the humerus flares to the medial and lateral epicondyles, with the medial epicondyle larger than the lateral (Fig. 16-1). The capitellum and the trochlea, the articulating surfaces for the radius and ulna, are located between the epicondyles. Separated from the trochlea by the trochlear groove, the capitellum serves as the lateral humeral articulating surface on the distal border of the lateral epicondyle. Unlike the trochlea, the dome-shaped capitellum does not extend to the posterior aspect of the humerus. Located immediately above the capitellum, the radial fossa is an indentation in the lateral epicondyle that accepts the radial head during elbow flexion. The distal end of the humerus is anteriorly rotated 30 degrees relative to the humeral shaft.

The ulna runs the length of the medial 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 (Fig. 16-2).

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 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.

Located on the thumb-side of the forearm, the radius is lateral to the ulna when the body is in the anatomical position. The proximal articulating surface, the radial head, is disk-shaped and concave to allow gliding and rotation on the capitellum, significantly enhancing the elbow’s stability.¹ The border of the proximal radius is also covered with articular cartilage to allow it to rotate on ...