A 20-year-old college football quarterback is evaluated in the emergency department for acute right shoulder pain. The patient sustained a blow to the arm an hour ago after he was tackled midthrow during a championship game. On physical examination, there is flattening of the right deltoid muscle and insensitivity of the overlying skin to pinprick. Peripheral pulses in the upper extremities are intact. Which of the following injuries is most likely responsible for this patient's findings?
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This patient with acute traumatic shoulder pain has flattening of the deltoid and paresthesia in the overlying skin, suggestive of a shoulder joint (ie, glenohumeral) dislocation. The glenohumeral joint is the most commonly dislocated joint in the body due to the shallow articulation between the humeral head and the glenoid fossa of the scapula. The humeral head may dislocate anteriorly, inferiorly, or posteriorly, but anterior dislocations are by far the most common.
Anterior shoulder dislocations classically follow a blow to an externally rotated and abducted arm (eg, throwing a football). Common examination findings include flattening of the deltoid prominence, protrusion of the acromion, and anterior axillary fullness (due to the humeral head's movement into this location). The axillary nerve is the nerve most commonly injured by anterior shoulder dislocations. It innervates the deltoid and teres minor muscles and provides sensory innervation to the skin overlying the lateral shoulder.
Shoulder dislocations are diagnosed on plain x-ray and are treated with prompt closed reduction, which typically improves the axillary neuropathy.
(Choice A) Acromioclavicular joint subluxation typically results from a downward blow to the tip of the shoulder and produces swelling and upward displacement of the clavicle. It is usually not associated with specific nerve injuries/deficits.
(Choice C) Clavicular fractures usually occur following direct trauma to the clavicle. Most fractures are in the middle third of the clavicle and produce local swelling and tenderness. Associated neurovascular damage is rare.
(Choice D) Fracture of the coracoid process of the scapula is rare. Individuals who engage in shotgun- or rifle-related activities are most commonly affected.
(Choice E) Rotator cuff tears may occur during shoulder dislocation but do not cause nerve injury. The rotator cuff is made up of the subscapularis, supraspinatus, infraspinatus, and teres minor muscles/tendons.
(Choice F) A spiral fracture of the midshaft humerus may result from torsion produced during a fall on an outstretched arm. Patients have swelling, bone crepitus, and ecchymoses of the arm. The radial nerve is commonly injured.
Educational objective:
Flattening of the deltoid muscle with acromial prominence after a shoulder injury suggests an anterior humerus dislocation. This injury most commonly results from a blow to an externally rotated and abducted arm. There is often associated axillary nerve injury, resulting in deltoid paralysis and loss of sensation over the lateral shoulder.