Edward B. Singleton Department of Diagnostic Imaging, Texas Children's Hospital, and Department of Pediatrics, Baylor College of Medicine, MC-2251, 6621 Fannin St, Houston, TX 77030, USA.
AJR Am J Roentgenol. 2012 Jan;198(1):194-9. doi: 10.2214/AJR.10.5730.
Previous studies have reported that contrast-enhanced sequences do not increase the sensitivity of MRI for the diagnosis of pediatric osteomyelitis and are not needed in the absence of edema on unenhanced MRI sequences. Invasive skeletal infections due to community-acquired Staphylococcus aureus are increasingly encountered in infants and young children and have a proclivity for involvement of both the unossified growth cartilage and the metadiaphyseal bone marrow of the extremities. The study objective is to assess the diagnostic efficacy of contrast-enhanced and unenhanced MRI sequences for the diagnosis of community-acquired S. aureus extremity skeletal infection in infants and young children.
A retrospective review was conducted of the clinical charts and imaging studies of patients younger than 18 months diagnosed with invasive community-acquired S. aureus skeletal infections from 2001 to 2009 at a large children's hospital. Sensitivity was calculated for the detection of skeletal infection on contrast-enhanced and unenhanced MRI sequences. The p values were calculated using the Fisher exact score method. The kappa value for interobserver reliability was determined.
Community-acquired S. aureus skeletal infections were noted in 34 extremity sites in 25 patients, five of whom had more than one site of disease. The affected skeletal sites were metaphyseal or metadiaphyseal bone marrow only in 16 cases (47%), unossified growth cartilage only in nine cases (26%), and both the unossified growth cartilage and metaphyseal or metadiaphyseal bone marrow in nine cases (26%). In seven of the nine cases of isolated involvement of the unossified growth cartilage, the cartilage appeared normal on unenhanced sequences and the diagnosis was made only by the demonstration of hypoenhancing or nonenhancing foci in the cartilage after gadolinium-based contrast agent administration. In five of the nine cases of infection of both the unossified growth cartilage and metaphyseal or metadiaphyseal bone marrow, neither the cartilage nor bone marrow appeared abnormal on unenhanced sequences. Therefore, 12 cases of skeletal infection would have been missed without the inclusion of contrast-enhanced sequences. Follow-up extremity radiographs were available for 10 patients, eight (80%) of whom exhibited growth disturbances.
Skeletal infection caused by community-acquired S. aureus in infants and young children manifests differently than in older children, including a propensity for involvement of the unossified growth cartilage and potentially occult nature of both cartilage and bone marrow involvement on unenhanced MRI sequences.
先前的研究表明，对比增强序列并不会提高 MRI 对小儿骨髓炎诊断的敏感性，并且在未增强 MRI 序列上没有水肿的情况下不需要使用。由社区获得性金黄色葡萄球菌引起的侵袭性骨骼感染在婴儿和幼儿中越来越常见，并且倾向于同时累及未骨化的生长软骨和四肢的干骺端骨髓。本研究的目的是评估对比增强和未增强 MRI 序列对诊断婴儿和幼儿社区获得性金黄色葡萄球菌四肢骨骼感染的诊断效能。
回顾性分析了 2001 年至 2009 年在一家大型儿童医院诊断为侵袭性社区获得性金黄色葡萄球菌骨骼感染的小于 18 个月的患者的临床病历和影像学检查。计算了对比增强和未增强 MRI 序列对骨骼感染检测的敏感性。使用 Fisher 精确得分法计算 p 值。确定了观察者间可靠性的 Kappa 值。
25 例患者中有 34 个肢体部位发现社区获得性金黄色葡萄球菌骨骼感染，其中 5 例患者有多个部位的疾病。受影响的骨骼部位仅为干骺端或干骺端骨髓的有 16 例（47%），仅为未骨化生长软骨的有 9 例（26%），同时累及未骨化生长软骨和干骺端或干骺端骨髓的有 9 例（26%）。在 9 例孤立性未骨化生长软骨受累的病例中，软骨在未增强序列上表现正常，仅通过在钆基造影剂给药后显示软骨内低增强或无增强灶做出诊断。在 9 例同时累及未骨化生长软骨和干骺端或干骺端骨髓的感染病例中，软骨和骨髓在未增强序列上均无异常表现。因此，如果不包括对比增强序列，将会漏诊 12 例骨骼感染。10 例患者可获得随访的肢体 X 线片，其中 8 例（80%）患者出现生长障碍。
婴儿和幼儿由社区获得性金黄色葡萄球菌引起的骨骼感染与年龄较大的儿童不同，包括未骨化生长软骨受累的倾向以及软骨和骨髓受累在未增强 MRI 序列上潜在的隐匿性。
