Differential diagnosis of septic hip arthritis in childhood by ultrasound examination.

The efficiency of ultrasound was tested in septic arthritis. A total of 259 children with hip pain, septic arthritis (n = 14), transient synovitis (n = 120), juvenile rheumatoid arthritis (n = 12), Legg-Calvé-Perthes disease (n = 92) and slipped capital femoral epiphysis (n = 21) were examined by ultrasound. By using the standard planes described by the DEGUM, it is possible to analyze the joint capsule, the surface of the femoral head and the periarticular structures. In cases with synovitis or joint effusion, capsular distention can be diagnosed by ultrasound. This distention is typical in septic arthritis, transient synovitis, juvenile rheumatoid arthritis, and in the onset phase of Perthes disease. Because capsular distention and osseous abnormalities in the various diseases are similar differentiation is not possible. Therefore, ultrasound cannot distinguish between septic and non-specific arthritis; capsular distention is a non-specific ultrasound sign. Immediate diagnostic puncture is necessary if septic arthritis is suspected (possible by ultrasound control). In cases with both capsular distention and osseous abnormalities, ultrasound usually allows differentiation between slipped capital femoral epiphysis/Perthes disease and septic/non-specific arthritis.