Teaching Case

The patient fell while playing football, sustaining an injury to his left arm and shoulder. He presented to accident and emergency with severe pain and restricted movement of the left upper limb. On inspection there was loss of the normal contour of the left shoulder, which looked 'flattened' compared with the opposite side, and he was supporting the left arm with the right hand.

The patient fell while playing football, sustaining an injury to his left arm and shoulder. He presented to accident and emergency with severe pain and restricted movement of the left upper limb. On inspection there was loss of the normal contour of the left shoulder, which looked 'flattened' compared with the opposite side, and he was supporting the left arm with the right hand. A clinical diagnosis of anterior shoulder dislocation was made and radiographs of the shoulder confirmed this diagnosis.

Anterior shoulder dislocation is at least 10 times more common than posterior shoulder dislocation and is rarely overlooked clinically or radiographically. The mechanism of injury is usually a fall onto the hand and anterior dislocation occurs when the arm is forcibly externally rotated and abducted. The head of the humerus is driven forward tearing the joint capsule or avulsing the glenoid labrum anteriorly. The humeral head usually comes to lie just below the coracoid process of the scapula. On the antero-posterior (AP) shoulder view the humeral head lies inferiorly and medial to the glenoid. The lateral scapular or Y-view shows the humeral head to be displaced anteriorly and not covering the glenoid as is normally seen. The axial (armpit) view is painful and often difficult to obtain when there is shoulder dislocation, but this also shows the head of the humerus anterior to the glenoid. There may be an associated fracture of the anterior lip of the glenoid (Bankart fracture), posterolateral aspect of the head of the humerus (Hill-Sachs deformity) or proximal humerus (neck or shaft). A Bankart lesion of the cartilaginous glenoid labrum and stripping of soft tissue from the glenoid neck would not be seen on conventional radiographs but CT arthrography and MRI demonstrate the degree of soft tissue damage as well as bony injury. Other complications of anterior shoulder dislocation include axillary nerve or arterial injury. Occasionally the posterior cord of the brachial plexus is injured. Reduction is usually performed under sedation but if there is an associated fracture of the proximal humerus, open reduction and internal fixation under general anaesthesia is necessary. It is essential to obtain post-manipulation films in order to confirm reduction, and also to exclude a fracture.