[Ultrasonography in the diagnostic approach of septic arthritis]

Septic arthritis is frequent in Tunisia and is responsible for orthopedic sequela. The purpose of this study was to establish the indication and the viability of ultrasound scanning in the early diagnosis of septic arthritis.

82 patients were explored by ultrasonography for suspected septic arthritis. Mean age was 7 years (range 2 months to 37 years). All sonographic studies were performed using a 7.5 MHZ transducer. 52 patients were surgically treated or had joint aspiration. Only 39 patients had septic arthritis. The hip and the knee were the most frequent localisation (respectively 20 and 12 cases).

Statistical analysis showed that the ultrasound scanning in the diagnosis of joint effusion had a sensitivity of 93.4 per cent and a specificity of 100 per cent. Matter floating within the joint effusion was noted in 50 per cent of septic arthritis. These changes were not found in other arthritis. The thickness of synovialis and joint capsule was not specific of septic arthritis. In hip septic arthritis (51 per cent of localisation) the mean width of the anterior synovial recess was 11.7 mm (5-20 mm). In the asymptomatic opposite hip, the mean width was 3.6 mm (2.6-5 mm). Cortical irregularities had suggested osteomyelitis of femoral neck in osteoarthritis of the hip in 4 cases. Subperiosteal abscess of the femoral neck was directly visualized in another patient.

Our expense highlights that sonography may be a useful tool in the management of patient with suspect septic arthritis. Sonography allows early diagnosis of joint effusion with high accuracy. Hyperechoĭc or mixed aspects of the fluid joint suggest septic origin.