A 6-year-old boy is brought to the emergency department by his father for elbow pain. He was riding his bicycle when he fell onto his outstretched right hand. He immediately clutched his right elbow in pain and began crying. He refuses to move his elbow. He has no medical problems and takes no medications. His temperature is 98.4°F (36.9°C), blood pressure is 108/64 mmHg, pulse is 100/min, and respirations are 20/min. On exam, the boy is holding his right wrist with his left hand and cries upon palpation of a region that is 2 cm proximal to his elbow. The radial head is palpated just distal to the lateral epicondyle. He is unable to make a pincer with his right thumb and index finger. When asked to hold a pen between his right thumb and index fingers, he drops it. The radial pulse is diminished on the right. Which of the following is the most likely diagnosis?
Distal radius fracture
Both bone forearm fracture
Supracondylar humerus fracture
Olecranon fracture
Supracondylar humerus fracture
This young patient presenting with elbow pain and associated signs of anterior interosseous nerve neurapraxia (inability to make pincer, weak pincer grasp) and vascular injury (diminished radial pulse) after a fall on an outstretched hand most likely has a supracondylar humerus fracture.

Supracondylar humerus fractures are one of the most common fractures seen in the pediatric population. This site is particularly prone to fracture due to the thin bone separating the coronoid and olecranon fossae in the supracondylar region. Due to the proximity of the brachial artery and median nerve, which course anteriorly, these structures are at risk for injury. Neurapraxia of the anterior interosseous nerve, which is a pure motor branch of the median nerve, presents as motor deficits in interphalangeal (IP) joint flexion of the thumb and distal IP joint flexion of the index finger. The radial and ulnar arteries are terminal branches of the brachial artery, which if injured results in diminished distal pulses. The diagnosis is made with anteroposterior and lateral view elbow radiographs. Radiographs will demonstrate the "fat pad sign" seen as a posterior fat pad that is indicative of fracture. Management depends on fracture type but can consist of cast immobilization (if minimally displaced with no neurovascular injury) or closed reduction and percutaneous pinning (for more displaced fractures).

Micheloni et al. reviews supracondylar fractures in children. They note it is the most common elbow fracture in the pediatric population. They recommend early and correct diagnosis and management to avoid early and late complications including neurovascular impairment and malunion.

Incorrect Answers:
Answer A: Both bone forearm fracture is another common pediatric fracture sustained from a fall, involving both the radius and ulna. It can be associated with neurovascular injury depending on the plane of deformity, but the location of the pain would be in the forearm, not proximal to the elbow.

Answer B: Distal radius fracture is a common fracture after a fall on an outstretched hand mechanism of injury. Neurovascular injury is possible, though uncommon. This patient’s pain is localized around his elbow, rather than near the distal radius. Often, a deformity can be visualized on exam.

Answer C: Monteggia fracture-dislocation is characterized by a proximal ulna fracture with radial head dislocation. It is commonly caused by direct trauma to the ulna. In contrast, this patient’s radial head is located inferior to the lateral epicondyle.

Answer D: Olecranon fracture is an uncommon pediatric fracture caused primarily by a fall onto the elbow in flexion. Median nerve and brachial artery injury are unlikely, given that these structures pass anteriorly in the cubital fossa.

Bullet Summary:
Supracondylar humerus fractures are common in the pediatric population and may present with elbow pain and concomitant median nerve and/or brachial artery injury.