CT findings of intraosseous gas in patients with osteonecrosis of maxillofacial region: a prospective study

Introduction: Intraosseous gas is a rare but significant radiological sign, primarily associated with emphysematous osteomyelitis (EO). Despite descriptions of similar cases in long bones and the spine, data on maxillofacial region (MFR) involvement are lacking in the literature. This study aims to address this gap, as the presence of intraosseous gas may indicate the presence of special pathogens and require a different therapeutic approach.

Objective: To evaluate the frequency, radiological features, and clinical significance of intraosseous gas in patients with MFR osteonecrosis.

Materials and methods: 93 patients diagnosed with M86.6 «Other chronic osteomyelitis» of the MFR with osteonecrosis of different etiology types (medication-related, post-radiation, post-COVID-19) were included in this study and were referred for multi-slice computed tomography (CT, Philips Incisive 64, China) using dental protocol with slice thickness 0.67 mm. During hospitalization a bacteriological examination of exudate or wound contents was performed with verification of the pathogen and determination of sensitivity to antibiotics and antimycotics.

Results: Intraosseous gas was detected in 29% (27/93) of patients including: 100% (4 cases) — post-COVID-19 osteonecrosis (4 patients); 28.6% (4 cases) — post-radiation osteonecrosis (14 patients); 25.3% (19 cases) — medication-related osteonecrosis (75 patients) due to bisphosphonate and/or denosumab therapy. Gas was most frequently associated with Enterobacter cloacae (33.3%, 9 cases), Klebsiella pneumoniae (25.9%, 7), and Escherichia coli (11.1%, 3). In 96% (46/48) of patients with streptococci, the intraosseous gas was absent.

Discussion: Key finding: Intraosseous gas is associated with fermenting bacteria (Enterobacter cloacae, Klebsiella pneumoniae, Escherichia coli), as confirmed by microbiological data in our study. In contrast, streptococci and non-fermenting microorganisms (Acinetobacter, Pseudomonas) predominantly do not cause gas formation. Detection of gas on MSCT is a marker of fermenting microbiota and warrants targeted antibiotic therapy.

Conclusion: Intraosseous gas is a significant diagnostic criterion, observed in 29% of patients with MFR osteonecrosis. When the intraosseous gas is detected, mandatory bacteriological testing with a focus on fermenting bacteria is required for planning an antibiotic therapy.

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