Imaging and clinical features of emphysematous osteomyelitis

To characterize the clinical and imaging features of emphysematous osteomyelitis (EO) in a single-center cohort and to expand upon existing literature, which is largely limited to isolated case reports.

This retrospective, IRB-approved study included patients identified through a PACS search for "intraosseous gas" or "intraosseous air" on CT or MRI from January 2014 to May 2025. Patients were excluded if intraosseous gas was attributable to trauma, open wounds, penetrating injury, or recent surgery. Clinical, laboratory, imaging, microbiologic, and histopathologic data were recorded.

Of 382 patients with intraosseous gas, 20 were included in the study. The mean age was 63 years, and 80% were male. Diabetes mellitus was present in 75% of patients. The foot was the most commonly involved site (75%). The "pumice stone" sign was observed in 50% of cases. Osseous erosions, periostitis and soft tissue emphysema were seen in 60%, 15% and 85% of patients, respectively. Radiographs were less sensitive than CT or MRI. Erythrocyte sedimentation rate and C-reactive protein were markedly elevated (mean 114 mm/hr and 210 mg/L, respectively). Among 14 culture-positive cases, 64% were polymicrobial, most originating from the foot. Surgical intervention was required in 83% of patients, including amputation in 67%.

EO is a rare, aggressive infection that primarily affects older patients with diabetes. The foot was the most common site, frequently associated with polymicrobial infection. Characteristic imaging features of osteomyelitis, such as erosion and periostitis, may be absent. Early recognition is essential, as most patients require surgical intervention.