The absence of hip joint effusion virtually excludes septic arthritis; a false negative rate of 5% has been described, noted in patients with a shorter duration of symptoms (<1 day) [40,43,45-47]. Hip US for the purpose of identifying joint effusion can be performed with high sensitivity and specificity [48]. In one study, nearly 80% of pediatric patients with septic arthritis of the hip required US imaging alone to guide their management [45]. US can also be used to identify joint fluid in extremity joints other than the hip. US in evaluation of osteomyelitis is limited in its ability to assess the osseous structures but can identify abutting inflammatory changes such as periosteal elevation, subperiosteal collections, and soft-tissue edema [40,49,50]. Bone Scan Whole Body and 3-Phase Bone Scan Area of Interest Skeletal scintigraphy has been traditionally used to accurately detect disease in cases of suspected acute osteomyelitis with normal radiographs because scintigraphic changes are present within the first 1 to 2 days of symptoms [8]. Although multiple studies have documented the success of scintigraphy in identifying acute osteomyelitis in children, there is limited data with studies in which only the area of interest was imaged. In one study in which blood pool and delayed imaging of only the area of interest were performed, 70 of 71 cases of osteomyelitis were identified [51]. However, multifocal osteomyelitis is common in the pediatric population, particularly among young children, and as a result, whole-body bone scan is typically advocated [52]. One study, in which a 3-phase bone scan was performed followed by a whole-body scan, delayed imaging noted 19% of cases of acute osteomyelitis were noted to be multifocal osteomyelitis, with over half of those cases noted in patients <6 years of age, the majority of which were neonates [52].
Osteomyelitis or Septic Arthritis Child Excluding Axial Skeleton PCAs. The absence of hip joint effusion virtually excludes septic arthritis; a false negative rate of 5% has been described, noted in patients with a shorter duration of symptoms (<1 day) [40,43,45-47]. Hip US for the purpose of identifying joint effusion can be performed with high sensitivity and specificity [48]. In one study, nearly 80% of pediatric patients with septic arthritis of the hip required US imaging alone to guide their management [45]. US can also be used to identify joint fluid in extremity joints other than the hip. US in evaluation of osteomyelitis is limited in its ability to assess the osseous structures but can identify abutting inflammatory changes such as periosteal elevation, subperiosteal collections, and soft-tissue edema [40,49,50]. Bone Scan Whole Body and 3-Phase Bone Scan Area of Interest Skeletal scintigraphy has been traditionally used to accurately detect disease in cases of suspected acute osteomyelitis with normal radiographs because scintigraphic changes are present within the first 1 to 2 days of symptoms [8]. Although multiple studies have documented the success of scintigraphy in identifying acute osteomyelitis in children, there is limited data with studies in which only the area of interest was imaged. In one study in which blood pool and delayed imaging of only the area of interest were performed, 70 of 71 cases of osteomyelitis were identified [51]. However, multifocal osteomyelitis is common in the pediatric population, particularly among young children, and as a result, whole-body bone scan is typically advocated [52]. One study, in which a 3-phase bone scan was performed followed by a whole-body scan, delayed imaging noted 19% of cases of acute osteomyelitis were noted to be multifocal osteomyelitis, with over half of those cases noted in patients <6 years of age, the majority of which were neonates [52].