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  When assessing a painful extremity, vascular compromise must be excluded first.

  
  
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  A patient who has fallen on an outstretched hand and has tenderness in the anatomical snuffbox of the wrist and a negative radiograph should have a thumb spica splint placed until a scaphoid fracture is definitively excluded.

  
  
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  Avoid nonsteroidal anti-inflammatory drugs after fractures. These medications inhibit bone healing.

  
  
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  In the upper extremity, compartment syndrome is most common in the forearm, especially after displaced supracondylar fractures in children.

Traumatic injuries to the upper extremity are common presenting emergency department (ED) complaints. It is the clinician’s objective to distinguish benign (eg, sprains, contusions) from emergent injuries (eg, open fractures, dislocations, vascular compromise). A systematic approach to identifying and classifying orthopedic injuries is needed to properly manage, treat, and disposition patients. This requires a thorough knowledge of orthopedic anatomy and function. The upper extremity contains several important articulations and long bones, which are at risk for dislocations and fractures during falls or by direct force.

Shoulder and Arm Injuries

The glenohumeral joint of the shoulder is the most mobile joint in the body and, unsurprisingly, the most commonly dislocated joint, accounting for 50% of all major dislocations seen in the ED. Anterior dislocations account for 95% of all shoulder dislocations (Figure 90-1). They occur most commonly when the arm is abducted, externally rotated, and extended and a posterior directed force is applied to the humerus. Axillary nerve injury is present in 12% of cases and is noted by testing sensation over the deltoid muscle and strength of abduction. Posterior dislocations are less common (5%) and present with inability to abduct and externally rotate. The classic mechanism that causes a posterior shoulder dislocation is a seizure.

Shoulder separation is a soft tissue injury to the acromioclavicular and coracoclavicular ligaments, which provide stability to the acromioclavicular joint. These typically occur after a fall with direct impact onto the shoulder and are divided by severity into first-, second-, and third-degree injuries. First-degree injuries are sprains of the acromioclavicular ligament without significant separation of the acromion and clavicle. Second-degree injuries are the result of complete disruption of the acromioclavicular ligament but an intact coracoclavicular ligament. Widening of the acromioclavicular joint is present on radiographs. Third-degree injuries occur when both ligaments are disrupted, producing widening of the acromioclavicular joint and cephalad displacement of the clavicle.

Humerus fractures occur anywhere on the shaft of the humerus (Figure 90-2). Fractures of the distal third of the humerus are associated with radial nerve injuries in 5–15% of cases.

Elbow Injuries

The elbow is the second most common large joint dislocation, 80–90% of which are posterior. Common elbow fractures include the radial head and olecranon in adults and the supracondylar humerus in children. Displaced supracondylar fractures in children are prone to developing compartment syndrome.

Forearm Injuries

A nightstick fracture is an isolated fracture of the ulnar shaft that occurs when a patient is protecting the body from a blunt force to the upper torso or head. Both bone forearm fractures (radius and ulna) are common in children after a fall. In both children and adults, these are highly unstable fractures that require early orthopedic consultation. Galeazzi fracture-dislocation is a distal radius fracture with dislocation of the ulna at the distal radioulnar joint (wrist). Monteggia fracture-dislocation is a proximal ulna fracture with dislocation of the radial head at the proximal radioulnar joint (elbow). Both of these injuries require surgical reduction.

Wrist and Hand Injuries

Distal radius fractures account for up to 15% of upper extremity fractures and are classified by the pattern of injury. They are most commonly caused by a fall on an outstretched hand FOOSH. A Colles fracture is an extra-articular metaphyseal fracture with dorsal angulation, as opposed to a Smith fracture, which is an extra-articular metaphyseal fracture with volar angulation (Figure 90-3). A Barton fracture involves the volar or dorsal rim of the distal radius with subluxation of the carpals. A Hutchinson fracture is an isolated fracture of the radial styloid.

Of the 8 carpal bones, the scaphoid accounts for 60–80% of all fractures (Figure 90-4). These fractures have a significant risk of avascular necrosis due to the pattern of blood supply in this area, and this risk increases with more proximal fractures. The false-negative rate of plain radiographs is as high as 20%, making conservative treatment in patients with tenderness over the scaphoid (anatomical snuffbox) appropriate.

Metacarpal fractures may occur in the base, shaft, neck, or head of the bone. The most common is a fracture to the neck of the fourth and/or fifth metacarpal, called a boxer’s fracture (Figure 90-5). Angulation is acceptable if it is <40 degrees. For fractures of the metacarpal shafts of the second and third metacarpal necks, less angulation (10–20 degrees) is acceptable because healing with significant angulation in these more anatomically fixed metacarpals may inhibit function.