Outcome of Septic Arthritis With Adjacent Osteomyelitis

Abstract

Source: Hamilton EC, Villani MC, Klosterman MM, et al. Children with primary septic arthritis have a markedly lower risk of adverse outcomes than those with contiguous osteomyelitis. J Bone Joint Surg Am. 2021;103(13):1229–1237. doi:10.2106/JBJS.20.01685Investigators from Children’s Health System of Texas and Texas Scottish Rite Hospital for Children, both in Dallas, TX, conducted a retrospective study to compare patient and clinical characteristics, hospital course, and outcomes between children with primary septic arthritis and those with osteomyelitis with contiguous septic arthritis. Study participants were identified by reviewing the medical records of patients with suspected septic arthritis who had been consecutively treated by a multidisciplinary team between 2009 and 2019. Children were classified as having primary septic arthritis if they had a hematogenous joint space infection and a pathogen identified by culture or PCR, without known or suspected contiguous osteomyelitis. Osteomyelitis was diagnosed based on clinical and radiologic findings, bone and/or bone aspirate/debridement cultures, and, in most cases, MRI. Patients with osteomyelitis in addition to septic arthritis constituted the osteomyelitis with contiguous septic arthritis group. Data abstracted from the medical records of study children included demographics, microbiology, radiographic and laboratory data, length of stay (LOS), ICU admission, and long-term complications (osteonecrosis, chondrolysis, physeal arrest, pathologic fracture, joint deformities, or need for joint replacement). Differences between children with primary septic arthritis and those with osteomyelitis with contiguous septic arthritis were compared using t-tests, Mann-Whitney U tests or chi-square tests.Data were analyzed on 134 children with primary septic arthritis and 105 with osteomyelitis with contiguous septic arthritis. Compared to those with primary septic arthritis, those with osteomyelitis with contiguous septic arthritis were older (mean ages 7.0 ±4.9 and 4.4 ±4.4 years, respectively; P <0.0001), had higher initial mean C-reactive protein levels (16.7 vs 7.8 mg/dL; P <0.0001), and lower initial mean platelet counts (290,000 vs 353,000 cells/mL; P = 0.0027). An MRI was obtained in 89.5% of children with osteomyelitis with contiguous septic arthritis and 34.3% of those with primary septic arthritis (P <0.0001). The most commonly identified bacterial pathogens in patients with primary septic arthritis were Staphylococcus aureus in 43 (32.1%) and Kingella kingae in 43 (32.1%). For those with osteomyelitis with contiguous septic arthritis, a bacterial etiology was identified in 94.3%; S. aureus was found in 77.1% of these children. ICU admission was more common in patients with osteomyelitis with contiguous septic arthritis than in those with primary septic arthritis (21.0% and 1.5%, respectively; P <0.0001), and LOS longer (mean values 13.0 ±11.9 and 5.3 ±4.2 days, respectively; P <0.0001). Complications were documented in 40 patients (38.1%) with osteomyelitis with contiguous septic arthritis vs 1 (0.7%) of those with primary septic arthritis.The authors conclude that children with primary septic arthritis can be distinguished from those with osteomyelitis with contiguous septic arthritis.Dr Hennrikus has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.Children with septic arthritis and osteomyelitis are at risk for adverse outcomes such as joint destruction, chondrolysis, growth disturbance, and osteonecrosis.1 Septic arthritis and osteomyelitis are part of a continuum of disease in which bacteria infect 1 or both foci.2 Historically, authors have proposed but not proven that the combination of septic arthritis with adjacent osteomyelitis is more problematic than simple isolated septic arthritis.3,4 The current investigators attempt to critically compare the outcomes and complications of primary septic arthritis with septic arthritis in combination with adjacent osteomyelitis.In the current study, children with septic arthritis and adjacent osteomyelitis were sicker and presented later. In addition, these patients were older, more often male, and had higher inflammatory marker values in the blood and lower platelet counts.Methicillin-resistant S. aureus was more commonly isolated in children with osteomyelitis compared to those with isolated septic arthritis. Patients with adjacent osteomyelitis needed more ICU care, more surgical procedures, and had longer LOS, longer antibiotic durations, and more re-admissions. Complications included eiphyseolysis and osteonecrosis in 1 patient with septic arthritis and pathologic fractures, chondrolysis, joint collapse, deformity, limb length inequality, and total joint replacement in patients with adjacent osteomyelitis.Based on the results of the current study, osteomyelitis appears to be the primary disease that potentiates osteonecrosis and joint destruction. In contrast to those with primary septic arthritis, children with adjacent osteomyelitis require longer duration of antibiotics and longer follow-up to ensure that adverse outcomes are recognized and addressed.5,6Septic arthritis plus adjacent osteomyelitis is a more severe disease than isolated septic arthritis. To ensure that a patient with septic arthritis does not have adjacent osteomyelitis, MRI is recommended for those with risk factors such as persistently elevated inflammatory markers and sustained S. aureus bacteremia. (See AAP Grand Rounds. 2021;45[2]:19.)7