Intraarticular osteoid osteoma: clinical features, imaging results, and comparison with extraarticular localization.

OBJECTIVE

Intraarticular osteoid osteoma is uncommon and presents diagnostic difficulties, which are important for both rheumatologists and orthopedic surgeons. Clinical symptoms, imaging procedures, differential diagnostic problems, and treatment results of intraarticular as compared with extraarticular osteoma are analyzed in this retrospective study.

METHODS

Nineteen patients with intraarticular osteoid osteomas (Group A), with a mean followup period of 34 months, are compared with 15 others with extraarticular lesions (Group B).

RESULTS

Nine intraarticular tumors were located in the hip, 3 in the elbow, 6 in the ankle, and one in the first metatarsal head. The nonspecific symptoms in Group A, such as chronic synovitis, decreased range of motion, joint effusion, contractures, and lack of the intense perifocal sclerotic margin on radiographs, led to significant delay in diagnosis (on average 26.6 mo in Group A, 8.5 mo in Group B). The extreme variety of previous diagnoses at referral reflect the problems of differential diagnosis. A detectable nidus is often absent on conventional radiograph. Bone scintigraphy is unspecific and often fails to visualize the nidus. Computed tomography scans were accurate in two-thirds of the intraarticular and in 90% of extraarticular cases. Magnetic resonance image findings, although sometimes controversial, provided essential additional information for the correct diagnosis and therapy.

CONCLUSION

Clinical symptoms and imaging signs of intraarticular osteoid osteomas were significantly different from the classical hallmarks of extraarticular lesions. The 10% intraarticular occurrence of osteoid osteomas in this series is not as rare as some investigators suggest. The radiological and clinical findings are uncharacteristic and misleading, and the lesions are difficult to identify. Careful search for history data, such as nocturnal pain and positive salicylate test, in addition to extensive imaging procedures, led to the correct diagnosis prior to surgery in two-thirds of our patients with intraarticular osteoid osteomas.