Clinical Cases - Joints of the Upper Limb

One evening while playing in the yard, a father picked up his four-year-old daughter by her hand and started swinging her around in a circle. At first the girl giggled, but all of a sudden, she cried out in pain. When her father put her down, he noticed that she was holding her elbow. Her arm was partially flexed and pronated, and she was unable to supinate her hand without considerable pain, so her parents took her to the emergency room. When the physician palpated her elbow, she found that the joint was tender, especially on the lateral side, but all of the bony landmarks were in their normal locations, leading the physician to suspect that the head of the radius had slipped out of the anular ligament. Radiographs proved inconclusive. Fairly certain of the diagnosis, however, the physician attempted to reposition the head of the radius by supinating the forearm fully and then flexing the elbow. She felt a small pop on the lateral side of the cubital fossa as the head of the radius slipped back into position and within a few moments the girl's elbow was as good as new.

Questions to consider:

1. What is the anular ligament and where is it located?

   The anular ligament is a circular ligament which forms a collar around the head of the radius, holding it firmly in place without directly attaching to the radius. This allows relatively free rotary movement of the radius at its proximal articulation with the capitulum of the humerus. The anular ligament is attached to the anterior and posterior margins of the radial notch on the ulna.

2. What are the bony landmarks that are readily palpable at the elbow?

   The olecranon process of the ulna, lateral and medial epicondyles of the humerus, and the head of the radius are generally readily palpable at the elbow. The three-dimensional relationships of these landmarks are important in diagnosing injuries to the elbow joint.

3. This sort of elbow dislocation (pulled elbow, or subluxation of the head of the radius) is common in pre-school aged children, whose radial heads are somewhat small relative to the size of the anular ligament. What other types of elbow dislocations are common and how do they present?

   Other common injuries to the elbow include:
   
   

   1. Posterior dislocation of the elbow: These are common in children and generally result from falling on an outstretched hand with the elbow flexed. These are easily recognized by unusual protrusion of the olecranon posteriorly along with displacement of the distal end of the humerus anteriorly, disrupting normal articulation with the forearm at the radial head and trochlear notch.
   2. Avulsion of the medial epicondyle: Also common in children, this injury results from a fall that causes severe abduction of an extended elbow. The ulnar collateral ligament, which is stronger than the fusion of the diaphysis and epiphysis of the humerus at the medial epicondyle, pulls the medial epicondyle away from the humerus. This epiphyseal plate does not usually fuse until around 20 years of age.
   3. Separation of the proximal radial epiphysis: This injury again happens only in children and is a displacement of the radial head following a fall that places a compression and abduction force on the elbow. This epiphysis usually fuses around 14-17 years of age. In adults, fractures of the elbow tend to occur more frequently than dislocations.

4. Why might the radiographs have been unhelpful in this situation?

   The radiographs probably were not helpful because this injury is not likely to tear the joint capsule and as a result, the head of the radius may not be obviously displaced on films. Furthermore, obtaining them was likely difficult in itself because of the age of the patient and the severity of pain caused by manipulation of the elbow.

5. What nervous structure is particularly vulnerable in elbow injuries and where is it located?

   The ulnar nerve, which passes behind the medial epicondyle and crosses the medial ligament of the elbow, is particularly vulnerable in elbow injuries. The ulnar nerve is often crushed in elbow injuries, which may lead to sensory loss and muscle weakness or paralysis in regions of ulnar distribution. Symptoms may appear immediately or after some delay. The effects of ulnar nerve damage are noticed particularly in the hand.

The goalkeeper in a soccer match fell on his outstretched left arm. He felt an immediate pain in the shoulder region and was unable to move his arm. At the hospital the arm was abducted and the deltoid muscle looked flat or hollow. The injured arm looked "too long", and there was intense pain on attempting to move the arm. A plain radiograph of the region showed that the humeral head was lying below the glenoid labrum and that there was no fracture of the humerus. The diagnosis was an anterior dislocation of the shoulder, and the orthopedic surgeon recommended Kocher's maneuver for management.

Questions to consider:

1. Why did the deltoid appear flat and hollow?
   

   Because of the downward displacement of the humeral head.

2. What neurovascular structures are liable to be injured in such a condition? How do you examine the patient to rule that out?
   

   The axillary nerve and the posterior humeral circumflex artery. Axillary nerve injury may be assessed clinically by examining skin sensation over the deltoid region, which is supplied by the upper lateral brachial cutaneous branch (C5) of the axillary nerve. Examining the deltoid will be difficult in dislocated shoulders.

3. What is the anatomical principle in reducing a dislocated shoulder?
   

   The elbow must be flexed under traction, humerus laterally rotated, adducted and then rotated medially. An X-ray is taken to ensure proper reduction, and axillary nerve function is assessed by asking the patient to abduct the shoulder.