As shoulder joints are unstable joints, strong posterior external forces leads shoulder dislocations in contact sports such as rugby, American football, and judo.
The shoulder joint typically is scapulohumeral joint, which consists of a round humeral head in the proximal part of the humerus (proximal position to the face) and the superficial glenoid fossa in the scapula. Because shoulder joints has wide range of motion, it has shallow bony structures and is reinforced around the joint with the joint capsule's ligaments and muscles (rotator cuff). However, when strong external force is applied by sports, it is easy to break and dislocated.
Cause and mechanism of occurrence
Cause of the injury
Injuries most occur in contact sports, such as rugby, American football, judo, and handball, and in falls caused by skiing or snowboarding.
If the shoulder joint is raised (lifted) and forced backward, or if the hand is pulled backward or the athlete falls on the back, the unstable humeral head may slide over and dislocate the articular surface. Most dislocations are anterior dislocations, in which the humerus head moves to the front of the body (Photo 1).
The first injury is caused by strong backward external forces, but after the second injury, those stopper structures (bones, ligaments, and joint capsule) can cause dislocations by even weaker external forces than the first injury. This tendency becomes more pronounced with each time, and even less external forces may cause re-dislocation (recurrent dislocations).
Rapid onset of pain, swelling, deformity, and limitation of motion, and complications which are blood circulation and nerve palsies (numbness of the shoulder and fingers) are found.
X-rays is used to diagnose the fitness of the articular surfaces. Recently, Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) examinations (Photo 2) have made it easier to determine the level of bone and soft tissue damage.
It also requires to see of the damage to the Bankart site (anterior to the inferior margin of the Bankart site: Glenoid cavity of the scapula, Photo 4) and the Hill-Sachs site (superior to the posterior aspect of the Hill-Sachs site: humeral head), which are critical for joint stabilization.
Photo 1 Left shoulder dislocation (white arrow indicates original bone head position)
Photo 2 MRI image after reduction.
Photo 3 Roentgenogram after reduction of left shoulder
Photo 4 Avulsion fracture of the joint edge. It is called Bankart site lesion
Treatment and rehabilitation
Treatment is generally divided into conservative treatment and surgical treatment. At the time of the first injury, after conservative manual reduction, the patient hangs down the upper arm, and with position of internal rotation in the shoulder joint, the patient undergoes immobilization by triangular bandage, so-called Desault bandage for fixation (Photo 5) for 3 to 4 weeks as conservative therapy for local restoration and stabilization. It also requires about 3 weeks of immobilization at the time of re-dislocation. Please note that, without adequate immobilization and appropriate rehabilitation the first time, repeated dislocations may occur.
Surgery is generally performed when the dislocation has recurred, and returning to contact competition takes about 6 months after surgery.
Photo 5 Desault fixation with sling.
Recurrent dislocations have a high recurrence rate within 2 years of the initial stage, and 60% of the patients have troubles of joints instabilities. (From 2014 American Orthopedic Association).
After the injury, the patient begins to exercise fingers and hands without affecting the site of the injury. One week after the injury, isometric exercises for adduction and internal rotation of the shoulder joint should be started. After 3 weeks, mild exercises should be performed within the 90° range of elevation of the shoulder joint. The key to rehabilitation right after dislocation is training the upper extremities in areas where the hands are in front of the body, with the back against walls and floors. Exercise with forward shoulder elevation abduction and external rotation should be prohibited until the last stage of rehabilitation (about 6 weeks).