Secondary radiological findings of osteoid osteoma as muscular atrophy and synovitis in paediatric and adult patients

Introduction
Diagnosis of osteoid osteoma may be delayed if secondary radiological findings such as muscle atrophy, oedema in peripheric soft tissue and bone marrow, joint effusion, or synovitis are more severe than the lesion itself. In this article, the purpose was to demonstrate secondary radiological findings of osteoid osteoma in both paediatric and adult patients. This study is one of the very few with such a large case series.

Material and methods
Radiological images of 152 patients were reviewed retrospectively. Peri-nidus sclerosis, periosteal reactive bone formation, bone marrow and soft tissue oedema, presence of synovial effusion, muscular atrophy in the affected extremity, osteopaenia, and posture deterioration were noted.

Results
Most of the lesions (87.5%) were localised in lower extremity bones. Among all the patients, 56% had extra-articular (65% in paediatric patients) and 44% had intraarticular (69% in paediatric patients) osteoid-osteoma. In 44% of the patients, synovial effusion was presented. In 89.4% of these, osteoid osteoma was localised in the joint. Of the 97 patients who had osteoid osteoma in lower extremities or pelvic bones, 73% had muscular atrophy. In 6% of them muscular atrophy was severe, and they had posture-gait disorder with accompanying osteopaenia. In 48% of the patients, there was reactive periosteal bone formation around the nidus.

Conclusions
Secondary radiological findings, such as muscular atrophy, synovitis, posture-gait deterioration, and reactive bone formation in a patient with continuous pain that is relieved by anti-inflammatory drugs may point to an osteoid osteoma.