Although some studies have shown no significant difference in sensitivity and specificity in diagnosis of osteomyelitis or septic arthritis with or without the use of gadolinium-based contrast agents, IV contrast has been shown to improve detection of abscesses [32,33]. Decreased femoral head enhancement on early postcontrast imaging has been noted as a reliable feature of septic arthritis not seen in transient synovitis, and diminished femoral head enhancement on MRI in the setting of septic arthritis in children <12 months of age correlated with development of secondary osteomyelitis [34,35]. Contrast has been shown to markedly improve detection of infection of unossified growth cartilage (chondritis) in children <6 years of age, in which the cartilage most commonly appeared normal on unenhanced sequences; hypoenhancement was more commonly noted with infection [36,37]. In one study of children <18 months of age with community acquired S aureus infection of the unossified epiphyseal cartilage, 7 of 9 cases demonstrated normal cartilage signal on noncontrast sequences; hypoenhancement or nonenhancement of involved foci was used for diagnosis [36]. In another study of children <6 years of age, focal or global cartilage nonenhancement was demonstrated in 71% of 14 patients with surgically confirmed epiphyseal osteomyelitis, compared with 21% of controls [37]. Global enhancement defects were more sensitive, noted in 43% of cases but not seen in any control cases. MRI Extremity Area of Interest In one study, a large field-of-view MRI was performed to encompass both lower extremities rather than the area of concern [38]. In patients who were later found to have osteomyelitis, 11% had contralateral extremity findings, including contralateral osteomyelitis, and 20% had ipsilateral septic arthritis.
Osteomyelitis or Septic Arthritis Child Excluding Axial Skeleton PCAs. Although some studies have shown no significant difference in sensitivity and specificity in diagnosis of osteomyelitis or septic arthritis with or without the use of gadolinium-based contrast agents, IV contrast has been shown to improve detection of abscesses [32,33]. Decreased femoral head enhancement on early postcontrast imaging has been noted as a reliable feature of septic arthritis not seen in transient synovitis, and diminished femoral head enhancement on MRI in the setting of septic arthritis in children <12 months of age correlated with development of secondary osteomyelitis [34,35]. Contrast has been shown to markedly improve detection of infection of unossified growth cartilage (chondritis) in children <6 years of age, in which the cartilage most commonly appeared normal on unenhanced sequences; hypoenhancement was more commonly noted with infection [36,37]. In one study of children <18 months of age with community acquired S aureus infection of the unossified epiphyseal cartilage, 7 of 9 cases demonstrated normal cartilage signal on noncontrast sequences; hypoenhancement or nonenhancement of involved foci was used for diagnosis [36]. In another study of children <6 years of age, focal or global cartilage nonenhancement was demonstrated in 71% of 14 patients with surgically confirmed epiphyseal osteomyelitis, compared with 21% of controls [37]. Global enhancement defects were more sensitive, noted in 43% of cases but not seen in any control cases. MRI Extremity Area of Interest In one study, a large field-of-view MRI was performed to encompass both lower extremities rather than the area of concern [38]. In patients who were later found to have osteomyelitis, 11% had contralateral extremity findings, including contralateral osteomyelitis, and 20% had ipsilateral septic arthritis.