Sonography of acute osteomyelitis in rabbits with pathologic correlation

Ultrasonography for the Detection of Osteomyelitis in Pediatric Patients With Soft Tissue Infection: A Pilot Study

OBJECTIVES

To demonstrate the usefulness of ultrasonography for differentiating soft tissue infections with or without osteomyelitis in pediatric patients who underwent ultrasonography and subsequent magnetic resonance imaging (MRI).

METHODS

Twenty-three patients were classified into 2 groups: 12 patients with and 11 patients without osteomyelitis based on MRI. Osteomyelitis using ultrasound is characterized by the presence of bone cortex irregularity and/or subperiosteal abscess formation. The diagnostic performance of ultrasonography for detecting osteomyelitis and subperiosteal abscess formation was compared with that of MRI. Diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were calculated with 95% confidence intervals (CIs).

RESULTS

Of 12 osteomyelitis cases, 11 had abnormal bone marrow enhancement (one residual case did not undergo contrast enhancement study) and 5 had subperiosteal abscesses. The diagnostic accuracy of ultrasonography for osteomyelitis was 82.6% (number of correct diagnosis of osteomyelitis/total number = 19/23; 95% CI, 61.2-95.0) and for detecting periosteal abscess was 95.7% (number of correct diagnosis of periosteal abscess/total number = 22/23; 95% CI, 78.1-99.9), respectively. The sensitivity and specificity of ultrasonography for detecting osteomyelitis were 66.7% (95% CI, 34.9-90.1) and 100% (95% CI, 71.5-100), respectively. The sensitivity and specificity of ultrasonography for detecting periosteal abscess were 80% (95% CI, 28.4-99.5), and 100% (95% CI, 81.5-100), respectively. One-third of osteomyelitis cases could not be detected using ultrasonography.

CONCLUSIONS

Ultrasonography may be useful for diagnosing osteomyelitis in pediatric patients; however, the technique appears limited by low sensitivity. However, it is more accurate for diagnosis of periosteal abscess in these patients.

US Evaluation of Juvenile Idiopathic Arthritis and Osteoarticular Infection

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.

Comparison of the diagnosis of plain radiography ultrasonography and magnetic resonance imaging in early diagnosis of acute osteomyelitis experimentally formed on rabbits

PURPOSE

We have compared the sensitivities of MRI, US and radiography which are some of the radiologic modalities used in the early diagnosis of acute osteomyelitis.

MATERIALS AND METHODS

After 1 week care and research on 20 New Zealand rabbits (average weight: 2.5 kg) in animal laboratory, study was begun. Six rabbits died after anesthesia and surgical procedure. There were 14 rabbits remaining and 10 of them formed the study group. Four of them were used as the control group. Fresh mouse feces was inoculated into the bone marrow of 20 tibia under general anesthesia and during the following 15 days, MRI, US and radiographic researches were made everyday.

RESULTS

According to the results that we got at the end of the 15-day period, MRI was found as the most sensitive method in describing early diagnosis of infection in the bone marrow and also in showing the extension of the infection to the soft tissue. Although US showed the findings later than MRI, it was determined that its sensitivity was less than but near MRI's in detecting subperiosteal fluid in short term period. Radiographic research gives acute osteomyelitis diagnosis latest, so it was determined as the modality that has the lowest sensitivity.

CONCLUSION

MRI which is one of the radiologic modalities among other diagnostic radiologic modalities that can be used in early diagnosis of acute osteomyelitis, has the highest sensitivity. Ultrasonography is the second most sensitive modality. Radiographic analysis has the least sensitivity among other modalities. As a result, first MRI then US and after that plain radiography should be used for the early diagnosis of acute osteomyelitis.

A regional approach to osteomyelitis of the lower extremities in children

Modem cross-sectional imaging, particularly MRI, has revolutionized the diagnosis and management of osteomyelitis in childhood. Diagnoses are made sooner, with greater confidence, and with better characterization of the extent of disease than possible on plain film grounds. Because the infection begins within the juxtaphyseal medullary bone, the MRI features are distinctive and frequently diagnostic of infection. Plain radiography continues to be an essential first step in the evaluation of suspected osteomyelitis and may on occasion be the only imaging study required for diagnosis and treatment. An understanding of the fundamental pathophysiology of osteomyelitis in the growing skeleton, in conjunction with the application of newer diagnostic imaging techniques, should continue to reduce the morbidity from this common pediatric problem.