Abstract

The osteoid osteoma is a benign bone lesion that accounts for 12.1% of benign tumors and 2.9% of all primary bone tumors. The third of the proximal femur is the most frequent location, followed by the tibia, the posterior elements of the spine and the humerus. The tumor, however, may be found in all parts of the skeleton. It affects more often males than females (2:1); 75% of patients are between 10 and 30 years of age. It is uncommon in children younger than 5 years and adults over 40 years.

The authors discuss the case of a 33-year-old man who undegoes arthroscopy of the ankle for a partial synoviectomy due to chronic synovitis.

Two years ago the patient underwent a surgical open intervention of reconstruction of the anterior talofibular ligament of the ankle, for an anterolateral instability of II degree following an ankle strain.

After that intervention, the patient has complained about the persistence of articular swelling with marked functional limitation, without benefit from conservative therapies.

During arthroscopy a large amount of hypertrofic synovial tissue is found, located in the anterior portion of the ankle. This tissue is removed and a biopsy is performed.

The bioptic sample is composed by synovial membrane with chronic flogosis and emosiderinic pigments and a “nidus” of osteoblastic benign proliferation related to an osteoid osteoma.

This patient therefore had a reactive chronic sinovitis secondary to a rare localization of osteoid osteoma.