Early Diagnosis of Pediatric Septic Hip Infection Using MRI

Khan et al. used systematic magnetic resonance imaging (MRI) to determine the prevalence of concomitant osteomyelitis (CO) in 58 consecutive pediatric patients with septic arthritis (SA) of the hip and assessed the influence of CO on clinical outcomes, the role of MRI, and the management of CO detected by MRI. Bacterial identification in the patients was routinely performed on joint fluid or bone aspirate samples from 2007 onward using both broad-range polymerase chain reaction (PCR) and Kingella kingae-specific real-time PCR. In their series of patients with SA, 43% also presented with CO, a prevalence that they noted was higher than the 33.2% prevalence in a systematic review1. Furthermore, a prevalence of only 16% would have been estimated by using only the radiographs in their series: most cases would have been missed without use of advanced imaging (MRI). Nevertheless, no significant therapeutic differences were observed between isolated SA and septic arthritis with CO in terms of the surgical burden, antibiotic duration, complications, or outcomes. They therefore concluded that the microorganism’s antibiotic susceptibility pattern and its virulence, rather than their MRI findings, were crucial to predicting the prognosis. This demonstrates the importance of early diagnosis and early treatment in pediatric hip SA regardless of the presence or absence of CO. At this time, MRI examination is preferable for the early diagnosis and detection of adjacent infectious foci, such as septic myositis around the hip, as well as for defining the extent of the disease and guiding personalized monitoring and counseling. However, early MRI is not always essential if it might delay prompt surgical intervention: such a delay may badly affect the vascular supply to the femoral head due to persistently high intra-articular pressure, and the avascular condition can produce various irreversible changes in the hip, leading to sequelae such as the septic necrosis of the femoral head2. As obtaining joint fluid aspirate for culture and checking clinical and laboratory parameters can be sufficient to make an immediate diagnosis prior to MRI and allow the development of an appropriate treatment strategy, they should take priority over MRI.