The pumice stone sign is a recently described distinctive imaging appearance of emphysematous osteomyelitis on CT described as clusters of greater than 3 distinct foci of intramedullary gas with irregularly irregular sizes ranging between 2 and 5 mm with resemblance to surface appearance of pumice stone. This sign is seen in 96% of cases of emphysematous osteomyelitis.1, 2
According to one study 1, most (79%) cases of emphysematous osteomyelitis were not associated with cortical destruction of bone unlike traditional osteomyelitis. Hence this sign may help in early diagnosis and treatment of this life-threatening condition. Adjacent soft tissue emphysema (79%) is also a key imaging feature.