A 2-year-old boy is brought to the emergency department due to high fever and malaise for the past 4 days. His parents say that he began limping yesterday and now refuses to walk. The patient has had no recent travel or exposure to anyone with similar symptoms. Temperature is 39.4 C (103 F). Passive range of motion of the hips, knees, and ankles does not elicit pain. There are no joint effusions. The patient refuses to bear weight. An intravenous radiotracer that localizes to areas of increased osteoblastic activity is administered, and several images are obtained to find areas with atypical activity. Abnormally increased uptake of the radiotracer is most likely to be seen in which of the following areas?

Question

A 2-year-old boy is brought to the emergency department due to high fever and malaise for the past 4 days.  His parents say that he began limping yesterday and now refuses to walk.  The patient has had no recent travel or exposure to anyone with similar symptoms.  Temperature is 39.4 C (103 F).  Passive range of motion of the hips, knees, and ankles does not elicit pain.  There are no joint effusions.  The patient refuses to bear weight.  An intravenous radiotracer that localizes to areas of increased osteoblastic activity is administered, and several images are obtained to find areas with atypical activity.  Abnormally increased uptake of the radiotracer is most likely to be seen in which of the following areas?

Quizplus · Accepted Answer

11ec160b_3a60_3e6c_9249_0fc1e92b612a_MD0001_00 This child has acute-onset fever, malaise, and refusal to bear weight, findings concerning for osteomyelitis. Older children often have focal bony tenderness, but children age ≤2 may be unable to localize pain. Passive range of motion of the joints typically is normal and helps distinguish osteomyelitis from septic arthritis. The most common cause of osteomyelitis in children is hematogenous spread of bacteria, which may be introduced by minor (often unnoticed) trauma to a distant site. Infection in children classically occurs in the metaphyses of long bones (eg, femur, tibia) because this region is highly vascular yet contains slow-flowing sinusoids that are conducive to bacterial seeding. Bacterial seeding within the metaphysis initially causes acute inflammation of the bone marrow, with focal hyperperfusion and increased radiotracer uptake within the affected region. Persistent inflammation within the confined bony space leads to increased intramedullary pressure, which compromises blood flow and forces infectious exudate into the cortex and periosteum. Without treatment, the infection can progress to chronic suppurative osteomyelitis, in which necrotic bone (ie, sequestrum) serves as an infectious reservoir and sinus tracts develop to drain away the purulent material. (Choice A) Osteomyelitis of flat bones (eg, skull, pelvis) is uncommon in children and is typically caused by contiguous spread of infection (eg, open wound, dental abscess). Although pelvic bone involvement may lead to refusal to bear weight, this patient has no gross abnormality of the hips or lower extremities suggesting adjacent soft tissue infection. (Choice B) Ewing sarcoma typically arises in diaphysis of the long bones, especially the femur. It is the second most common malignant bone tumor in children after osteosarcoma. However, Ewing sarcoma typically presents in children age >10 with an insidious onset of progressive pain, not in toddlers with acute refusal to bear weight. (Choice C) The physis (growth plate) in children limits vascular connections between the metaphysis and epiphysis, which is relatively less vascularized, making epiphyseal involvement uncommon in hematogenous osteomyelitis. Although avascular necrosis of the proximal femoral epiphysis (eg, Legg-Calve-Perthes) can present with a limp, the pain is typically more mild and develops gradually without fever. (Choice E) Hematogenous osteomyelitis in adults occurs more commonly in the vertebral bodies due to increasing vertebral vascularity with age as well as epiphyseal closure during puberty (improves capillary flow within the metaphyses of long bones). Educational objective: Hematogenous osteomyelitis occurs most commonly in children. It usually affects the metaphysis of long bones due to the presence of slow-flowing sinusoids that are conducive to bacterial seeding. Fever and refusal to bear weight are common manifestations in young children who are unable to localize the pain. __________ References: Hematogenous osteomyelitis in infants and children: imaging of a changing disease. (http://www.ncbi.nlm.nih.gov/pubmed/28514223) Haematogenous acute and subacute paediatric osteomyelitis: a systematic review of the literature. (http://www.ncbi.nlm.nih.gov/pubmed/22529075)

A 2-Year-Old Boy Is Brought to the Emergency Department Due