SYNOVIAL HEMANGIOMA - IMAGING FEATURES IN 8 HISTOLOGICALLY PROVEN CASES, REVIEW OF THE LITERATURE, AND DIFFERENTIAL-DIAGNOSIS

Objective. This study was undertaken to describe the imaging character istics of synovial hemangioma, with the goal of improving the disappoi nting rate (22%) of clinical diagnosis of this condition. A review of the literature and the differential diagnosis of intra-articular lesio ns, including synovial osteochondromatosis and pigmented villonodular synovitis, are also presented. Patients. The subjects of the study wer e 8 patients (4 males, 4 females; age range: 5-47 years; mean age: 19 years) with histologically confirmed synovial hemangioma involving the knee (n=7) or wrist (n=1). We retrospectively examined the imaging st udies performed in these patients, including plain radiography (n=8), magnetic resonance imaging (MRI; n=4), angiography (n=3), arthrography (n=2), and contrast-enhanced computed tomography (CT; n=2). Results. Plain radiographs showed a soft tissue density suggesting either joint effusion or a mass in all patients. Phleboliths and bone erosions on plain films in four patients with extra-articular soft tissue involvem ent pointed to the correct diagnosis. Angiography, showing fine-calibe r, smooth-walled vessels, contrast pooling in dilated vascular spaces, and early visualization of venous structures, was diagnostic in two p atients. Neither arthrography nor CT yielded specific enough findings. MRI was consistently effective in allowing the correct diagnosis to b e made preoperatively, showing an intra-articular or juxta-articular m ass of intermediate signal intensity on TI-weighted images and of high signal intensity on T2- or T2-weighted images with low-signal channe ls or septa within it, A fluid-fluid level was found in two patients w ith a cavernous-type lesion. Conclusion. Despite the limited nature of this study, it shows clearly that MRI is the procedure of choice when ever an intra-articular vascular lesion such as synovial hemangioma is suspected. Nonetheless, phleboliths and evidence of extra-articular e xtension on plain radiographs point to angiography as an effective pro cedure of first resort because it can be combined with embolotherapy.