Crystal-associated synovitis- ultrasonographic feature and clinical correlation.

The aim of this paper is to describe the ultrasonographic findings in rheumatologic pathology due to crystal deposition. There are four main types of crystals involved: monosodium urate, calcium pyrophosphate dihydrate, basic calcium phosphate (hydroxyapatite), and calcium oxalate. In gout the joint fluid is anechoic only at the first gouty attack; afterwards the synovium begins to proliferate. Double contuour sign, a focal or diffuse enhancement of the superficial margin of the articular cartilage is a specific finding. Bursitis has chronic features from the beginning. The ultrasonographic aspect of tophi depends on their age and size (at first small, hypoechoic and homogenous nodules, then echoic with hyperechoic edges and finally pseudotumoral, inhomogeneous). The depositions in the superficial layer are hyperechoic, well delimited only in the absence of inflammatory reaction. The depositions at the entheseal level are leading to the gouty enthesopathy. In knee involvement irregularities of the anterior surface of patella are found. In chondrocalcinosis the most important ultrasonographic signs are the thin hyperechoic band, parallel to the surface of the hyaline cartilage and the punctuated pattern of the fibrocartilage. In hydroxyapatite associated disease, calcifications are frequent in the shoulder or in the great trochanter of the hip, with aspects depending of the calcification phase. Milwakee shoulder is an advanced form of this pathology, associated with rotator cuff arthropathy. Oxalate crystal deposition disease is seen rarely, in patients with primary hyperoxaluria and in patients with end-stage renal disease. Therefore ultrasonography is useful in characterize the articular and juxta-articular alterations in crystal related diseases.