Posterior Glenohumeral Dislocations

Posterior dislocation may occur with the humeral head in the subacromial (most commonly with the humeral head behind the glenoid and beneath the acromion), subglenoid, or subspinous. The latter two are rare.

The usual mechanism is an indirect force that produces forceful internal rotation and adduction. This mechanism may occur during a fall or from violent muscle contraction from a seizure or electric shock. Direct force to the anterior shoulder can also produce a posterior dislocation.

Posterior dislocations are reported to be commonly missed. Thus, a careful examination and radiographic evaluation are essential. Clinical findings include the following:

1. The arm is adducted and internally rotated.

2. The anterior shoulder is flat and the posterior aspect full.

3. The coracoid process is prominent.

4. The patient will not allow external rotation or abduction because of severe pain.

Although the anteroposterior radiograph is helpful, the scapular Y radiograph is diagnostic. In this radiograph, the humeral head is seen in a posterior position.

Since severe pain and muscle spasms are the norm, muscle relaxation and analgesia are paramount. The reduction is performed with the patient supine. Traction is applied to the adducted arm in the long axis of the humerus. An assistant gently pushes the humeral head anteriorly into the glenoid fossa.

Most complications are fractures, including fractures of the posterior glenoid rim, humeral head (reversed Hill-Sachs deformity), humeral shaft, and lesser tuberosity. Neurovascular and rotator cuff tears are less common than in anterior dislocations.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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