A 3-year-old boy is brought to the emergency department for refusal to move his right arm. This afternoon, he tripped while holding hands with his sister, who pulled up on his arm to prevent him from falling. The patient immediately began to cry and has since refused to move the arm. On physical examination, he holds the right arm against his abdomen with the elbow flexed and forearm pronated. The patient cries with any attempted manipulation of the right elbow. There is no visible swelling or deformity. Which of the following structures is most likely affected in this patient's condition?

Question

A 3-year-old boy is brought to the emergency department for refusal to move his right arm.  This afternoon, he tripped while holding hands with his sister, who pulled up on his arm to prevent him from falling.  The patient immediately began to cry and has since refused to move the arm.  On physical examination, he holds the right arm against his abdomen with the elbow flexed and forearm pronated.  The patient cries with any attempted manipulation of the right elbow.  There is no visible swelling or deformity.  Which of the following structures is most likely affected in this patient's condition?

Quizplus · Accepted Answer

11ec160b_35ed_c9d8_9249_577274b5dae6_MD0001_00 This patient's mechanism of injury (eg, sudden pulling up on the arm) and presentation (eg, holding the arm flexed and pronated, pain with movement) are consistent with radial head subluxation (ie, nursemaid's elbow). The radial head is anchored to the ulna by the annular ligament, which encircles the proximal radius. In children age <5, this tissue is relatively thin compared to older children and adults. Sudden axial traction (eg, pulling up on the arm by the hand) or twisting can cause the annular ligament to slip over the radial head and become entrapped in the radiohumeral joint. Patients classically hold the affected arm close to the body with the elbow flexed and the forearm pronated. There is significant pain with movement or manipulation of the joint but typically no obvious swelling or deformity. Reduction can usually be accomplished either by hyperpronation of the forearm or supination of the forearm with flexion of the elbow. (Choice B) A distal biceps tendon rupture characteristically occurs in older patients after forceful extension of the elbow while the biceps muscle is contracted, resulting in a visible mass in the mid-upper arm (ie, "Popeye" deformity). (Choice C) The interosseous membrane is a broad sheet of connective tissue between the radius and ulna that provides forearm stability and a point of attachment for the forearm muscles. Injury to the membrane is associated with fracture of the radius or ulna after a fall onto an outstretched hand. (Choice D) Injury to the radial (lateral) collateral ligament of the elbow can occur with acute varus stress during a fall onto an outstretched hand and is often associated with fracture or dislocation of the elbow. (Choice E) The ulnar (medial) collateral ligament is typically injured by intense, repetitive overuse involving a valgus stress at the elbow (eg, pitching a baseball), resulting in medial elbow pain that increases during throwing motions. Educational objective: Radial head subluxation (ie, nursemaid's elbow) is the displacement of the annular ligament into the radiohumeral joint, classically resulting from sudden axial traction (eg, pulling) on the arm of a child age <5. Although most patients do not have any obvious swelling or deformity, they avoid moving the arm due to pain and hold it with the elbow flexed and forearm pronated. __________ References: Common paediatric elbow injuries. (http://www.ncbi.nlm.nih.gov/pubmed/29290878)

A 3-Year-Old Boy Is Brought to the Emergency Department for Refusal