Because of its relatively fixed position at posterior cord and at deltoid, any downward subluxation of proximal humerus can result in traction and injury to the axillary nerve. Additionally, its close relationship to the inferior capsule makes it susceptible to injury with anterior dislocations. Patients with this injury will display loss of shoulder abduction and external rotation.
Patients with anterior dislocations rarely can have axillary artery damage. Blunt trauma to shoulder, such as a direct blow to the shoulder girdle is often the mechanism of injury, as the axillary artery may be stretched. This artery can also be injured through forceful closed reduction of long-standing anterior shoulder dislocation. Furthermore, injury is increased in patients with atherosclerotic disease. It should be further clarified that the posterior circumflex artery branches from the axillary artery and may be damaged first before the tension occurs on the axillary artery.
The most commonly torn rotator cuff tendon is the supraspinatus tendon, which is the tendon on the top of the shoulder joint, and is also commonly injured with anterior shoulder dislocation. When this tendon tears, it can cause pain in the front and on the side of the shoulder.
The humeral head is forced anteriorly, out of the glenohumeral joint, tearing the shoulder capsule and detaching the labrum from the glenoid. This strains the anterior band of the glenohumeral ligament, often tearing it. This lesion may lead to pain and patients displaying arm abduction and external rotation. This lesion is closely related and a part of Bankart’s lesion.
Bankart’s lesion is the avulsion of the antero-inferior glenoid labrum at its attachment to the antero-inferior glenohumeral ligament complex. There is rupture of the joint capsule and inferior glenohumeral ligament injury.
Hill-Sachs lesion is a posterolateral humeral head indentation fracture, which can occur as the soft base of the humeral head impacts against the relatively hard anterior glenoid. This occurs in 35-40% of anterior dislocations and up to 80% of recurrent dislocations.
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