US Evaluation of Juvenile Idiopathic Arthritis and Osteoarticular Infection

Abstract

Juvenile idiopathic arthritis (JIA) and osteoarticular infection can cause nonspecific articular and periarticular complaints in children. Although contrast material-enhanced magnetic resonance imaging is the reference standard imaging modality, musculoskeletal ultrasonography (US) is emerging as an important adjunct imaging modality that can provide valuable information relatively quickly without use of radiation or the need for sedation. However, diagnostic accuracy requires a systemic approach, familiarity with various US techniques, and an understanding of maturation-related changes. Specifically, the use of dynamic, Doppler, and/or multifocal US assessments can help confirm sites of disease, monitor therapy response, and guide interventions. In patients with JIA, ongoing synovial inflammation can lead to articular and periarticular changes, including synovitis, tenosynovitis, cartilage damage, bone changes, and enthesopathy. Although these findings can manifest in adult patients with rheumatoid arthritis, important differences and pitfalls exist because of the unique changes associated with an immature and maturing skeleton. In patients who are clinically suspected of having osteoarticular infection, the inability of US to evaluate the bone marrow decreases its sensitivity. Therefore, the US findings should be interpreted with caution because juxtacortical inflammation is suggestive, but neither sensitive nor specific, for underlying osteomyelitis. Similarly, the absence of a joint effusion makes septic arthritis extremely unlikely but not impossible. US findings of JIA and osteoarticular infection often overlap. Although certain clinical scenarios, laboratory findings, and imaging appearances can favor one diagnosis over the other, fluid analysis may still be required for definitive diagnosis and optimal treatment. US is the preferred modality for fluid aspiration and administering intra-articular corticosteroid therapy. RSNA, 2017.

Non-traumatic Musculoskeletal Diseases in Children

“…Paravertebral soft tissue extension (including abscesses) can also be easily seen. [14,16,18] Intra-articular infections in children are most commonly caused by hematogenous spread of microorganisms into the joints. However, in infants direct extension into the joint space from adjacent osteomyelitis can also cause septic arthritis, due to the diaphysial vessels that still penetrate the growth plate to reach the epiphysis.…”

Imaging of Pediatric Growth Plate Disturbances

“…Similar to the periosteum, the perichondrium is hypointense with all MR imaging pulse sequences. In contrast to the periosteum, however, the perichondrium is tightly attached to the underlying growth plate, acting as a barrier to the epiphyseal spread of metaphyseal subperiosteal pathologic processes (13,14). The perichondral vessels supply the perichondrium and most peripheral aspects of the growth plate (Fig 1), making the central growth plate relatively vulnerable to insult.…”

“…The growth plate injury can be direct or indirect, depending on the child's stage of development and the infectious organism. In infants, transphyseal vascular channels allow the spread of hematogenous infection from the metaphysis into the epiphysis (14). Epiphyseal infection, if severe enough, can cause epiphyseal ischemia that may indirectly injure the growth plate (97) (Fig 14).…”

The Acutely Limping Preschool and School-Age Child: An Imaging Perspective

“…Although contrast-enhanced MRI is the imaging study of choice, ultrasound is an emerging adjunct modality that helps confirm disease sites, monitors response to therapy, and guides interventions such as joint fluid aspiration and administration of intra-articular steroids. 37 Plain radiographs are only of value in more advanced stages of the disease, once osseous erosions and cartilage destruction have occurred.…”