Diagnosing Osteomyelitis in Children

Clinical Presentation

The American College of Radiology recommends that osteomyelitis be considered in young children, with half of cases reported in children under 5 years of age, often with a history of trauma and a limp as the primary symptom 1
The American College of Radiology states that hematogenous bacterial seeding is the most common cause of osteomyelitis, and Staphylococcus aureus is the most common causative organism 1
Children under 2 years are more likely to have septic arthritis than osteomyelitis, while those between 2-10 years have slightly more osteomyelitis than septic arthritis, according to the American Academy of Pediatrics 3

The American College of Radiology suggests that plain radiographs should be the initial imaging test, though they are often not diagnostic in acute osteomyelitis, and can provide anatomic evaluation and suggest alternative diagnoses such as fracture or tumor 4

The American College of Radiology recommends MRI as the modality of choice for suspected bone infections due to its high sensitivity (82-100%) and specificity (75-96%), and excellent soft tissue contrast and delineation of anatomic detail 1, 2, 4
MRI findings suggestive of osteomyelitis include decreased T1-weighted bone marrow signal, increased signal on fluid-sensitive sequences, and subperiosteal fluid, which is a distinguishing feature of osteomyelitis 1, 4

The American College of Radiology states that ultrasound is highly sensitive for diagnosing joint effusion, particularly in the hip, and can detect hip effusions as small as 1 mL 2
The absence of hip joint effusion virtually excludes septic arthritis, with a false negative rate of only 5% 2

The American College of Radiology recommends image-guided aspiration of affected joint or bone for definitive diagnosis, with aspirated fluid sent for Gram stain, culture, cell count, and crystal analysis 5, 7
Blood cultures should be obtained before initiating antibiotic therapy, according to the Infectious Diseases Society of America 7

The American College of Radiology notes that children with sickle cell disease pose a diagnostic dilemma because marrow infarction and osteomyelitis may present similarly, and concomitant osteomyelitis and septic arthritis are common in children and may occur in >50% of cases 1, 3, 6
Contrast-enhanced MRI improves detection of abscesses and infection of unossified growth cartilage (chondritis) in children under 6 years, according to the American College of Radiology 1