Fibrous dysplasia is a genetic not hereditary disease of the skeleton, most frequently located at the femoral bone. The extension and the radiographic morphology of the femoral lesion are variable, and the prognosis is unpredictable. The purpose of this study is to propose a radiographic classification of the femoral lesion, related to the prognosis and the natural history of the disease.

The authors reviewed the radiographic examinations of 25 patients affected by fibrous dysplasia of bone with femoral involvement, who were followed-up at least two years after diagnosis. Eleven patients had bilateral localization of the disease, for a total of 36 affected femurs. A radiographic classification of the femoral lesion was proposed based on the localization, the extension and the type of the lesion.

The authors classify the femoral lesions as lytic, lytic with surrounding sclerosis, lytic and sclerotic, sclerotic and complex. They observed a prevalence of the lytic lesions and involvement of the proximal part of the femur. Many lesions (40%) expanded with age, and the sclerotic component also increased. The lytic lesions worsened with age, causing severe deformity of the femur. However the mostly sclerotic lesions turned out to be stable at follow-up. The worsening of the lesion was not related to the sex of the subjects; 77% of the worsened lesions were observed in patients younger than 20 years of age, while 66% of the stable lesions were found in patients older than 20 years.

In conclusion, this study demonstrated that the prognosis of the femoral lesion in fibrous dysplasia is related to the type of lesion, as per the radiographic classification here in described. Prognosis is also related to the age of the patient and the presence of a sclerotic component, which suggested a greater stability of the lesion.