[Technique and value of arthrosonography in rheumatologic diagnosis. 2: Ultrasound diagnosis of the hip area].

The clinical investigation of the hips in patients with rheumatic diseases is often equivocal. Thus, ultrasonography of this region is very relevant for rheumatologists. We suggest following standard scans: 1) anterior longitudinal scan to detect synovitis of the hip joint, iliopectineal bursitis, irregularities of the bone surface in osteoarthritis, Perthes' disease, and erosions due to inflammatory disease, 2) anterior transverse scan to evaluate these structures in an additional dimension, 3) lateral longitudinal scan of the hip joint with the same objective as the above mentioned scans; 4) lateral longitudinal scan, and 5) lateral transverse scan of the greater trochanter to diagnose trochanteric bursitis and bone irregularities due to enthesiopathy, and 6) dorsal oblique scan (optional) to diagnose hip joint effusions and pannus that localize in the dorsal region. Rotation of the joint is necessary to detect small effusions. The transducers should have a medium frequency of 5 to 7.5 MHz. In obese or muscular patients, 3.5 MHz transducers may be necessary to increase penetration. The anterior distance between the bone and the joint capsule of the hip joint is > or = 7 mm in probable and > or = 8 mm in definite synovitis or effusions. Synovitis or effusions are probable if the difference between right and left hip is > or = 2 mm, and they are definite if the difference is > or = 3 mm.