A series of radiological changes are seen in mycetoma. This is due to the fact that all mycetoma agents are osteophilic and it may be due to the effect of the granuloma on both the affected bone and its blood supply.
In early disease, the radiography is essentially normal. Eventually with the development of the granuloma in size, a soft tissue mass with obliteration of fascial planesmay be seen. The granuloma, is shown as a dense shadow or as scattered multiple soft tissue shadows. Calcification and obliteration of the fascial planes may sometimes be seen as the disease progresses, the cortex may be compressed from outside by the granuloma leading to bone scalloping, this is followed by a variable amount of periosteal reaction. Periosteal new bone spicules are laid down at right angle to the cortex to create a sun-ray appearance and Codman triangle, an appearance that may be undistinguishable from that due to osteogenic sarcoma.
Late in the disease, there may be multiple punched out cavities through the normal density of the bone. These cavities are large in size, few in number with well-defined margins in eumycetoma. Whereas, the bone cavities in actinomycetoma are usually smaller in size, numerous and have no definite margins. The cavities are produced by the replacement of the osseous tissue by the grains. Their size is due to the size of the grains of the causative organism. The cavities are usually filled with solid masses of grains and fibrous tissue, which provides bone support. This may explain the rarity of pathological fractures in mycetoma. The bony changes in the skull are unique: they are purely sclerotic with dense bone formation and loss of trabeculation.
Osteoporosis at and distal to the affected part is well observed in mycetoma and this may be due to disuse atrophy or due to the compression of the bone and its blood supply by the mycetoma granuloma.
Chemotherapy causes radiological improvement consisting of remoulding, absorption of the sclerotic bone and reappearance of the normal trabecular pattern.
In a retrospective study of 516 patients seen at the Mycetoma Research Centre, Sudan, a tertiary center, only 3% had a normal radiograph. The most common abnormalities were soft tissue swelling (93%), bone sclerosis (56%), and bone invasion (46%). Other abnormalities included bone cavities (32%) and osteoporosis (19%).