A 2-year-old girl is evaluated in the emergency department for refusal to move her right a… — USMLE Step 2 CK

A 2-year-old girl is evaluated in the emergency department for refusal to move her right arm. Approximately three hours ago, she was holding hands with her older brother and suddenly tripped; the brother quickly pulled her up by the hand to prevent her from falling. Following this event, she began crying and has kept her right arm tucked against her torso. On physical examination, the patient's right elbow is held in slight flexion and the forearm is pronated. There is no visible ecchymosis, erythema, or localized edema. She exhibits marked resistance and distress upon attempted passive supination of the right forearm, but no focal tenderness is elicited over the clavicle, distal humerus, or wrist. Her vital signs are stable, including a temperature of $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ) and a heart rate of $110/\text{min}$ . Laboratory testing shows a leukocyte count of $7,500/\text{mm}^3$ , an erythrocyte sedimentation rate (ESR) of $8\text{ mm/hr}$ , and a C-reactive protein (CRP) level of $2\text{ mg/L}$ . Which of the following is the most appropriate next step in management?

A
Obtain anteroposterior and lateral radiographs of the right elbow
B
Recommend oral acetaminophen and supportive care at home
C
Administer intravenous cefazolin and admit for observation
Perform closed reduction of the radial headAnswer
E
Apply a long-arm posterior splint and arrange orthopedic follow-up

Answer

The most appropriate next step in management is to perform a closed reduction of the radial head.

This patient presents with a classic history and physical examination for radial head subluxation, commonly known as Nursemaid's elbow. This is a very frequent pediatric injury occurring primarily in children aged 1 to 4 years. It is caused by sudden axial traction applied to a pronated and extended forearm (e.g., pulling a child by the hand to prevent a fall). This force causes the annular ligament to slip over the head of the radius and become trapped in the radiohumeral joint. Clinically, the child refuses to use the arm, holding it slightly flexed and pronated, and strongly resists passive supination. Crucially, there is no focal bone tenderness, swelling, or signs of infection (the patient is afebrile with normal WBC, ESR, and CRP). Because the presentation is classic and there are no signs of a fracture or infection, the diagnosis is purely clinical. The most appropriate next step is immediate closed reduction, typically achieved via the hyperpronation technique or the supination-flexion technique. Radiographs are not required prior to reduction unless the presentation is atypical, there is significant swelling, or the reduction attempt fails.

Step-by-Step Solution

Analyze the patient's history and mechanism of injury.

A 2-year-old child presents with sudden arm immobility after experiencing axial traction on a pronated arm.

This establishes the classic mechanism for radial head subluxation (Nursemaid's elbow).

Evaluate the physical examination and laboratory findings.

The arm is held in flexion and pronation. There is no focal tenderness, swelling, or deformity. Inflammatory markers (WBC, ESR, CRP) and temperature are normal.

This rules out fractures (which would have swelling/focal tenderness) and infectious etiologies like septic arthritis (which would present with fever and elevated inflammatory markers).

Determine the appropriate management protocol based on the clinical diagnosis.

Immediate closed reduction of the radial head.

When the history and physical exam are classic for Nursemaid's elbow, the diagnosis is purely clinical and radiographic imaging is not required prior to reduction.

Key Concept

Diagnosis and management of radial head subluxation (Nursemaid's elbow)

Alternative Method

While the traditional supination-flexion maneuver is widely taught, the hyperpronation technique (applying pressure to the radial head while hyperpronating the forearm) is often preferred as the first-line approach due to a higher first-attempt success rate and being perceived as less painful for the child.

Estimated Time:1m 0s

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