To explore the ultrasound manifestations of septic hip arthritis in neonates and infants, and evaluate its role in early diagnosis, treatment, and follow-up.

Twenty-two cases of neonates or infants less than 6 months old who were diagnosed as having septic hip arthritis at Shenzhen Children's Hospital from January 2015 to January 2021 were selected to retrospectively analyze the clinical data, main ultrasonic manifestations, and imaging characteristics of septic hip arthritis, as well as the treatment outcome and ultrasonic follow-up results.

A total of 22 patients with septic hip arthritis were analyzed, including 8 males and 14 females, with a median age of 52 days (range, 1-180 days). Ultrasonic findings of the hip joint included hip joint synovial thickening and joint cavity effusion in 21 cases (22 hip joints) , including 14 cases (15 hip joints) of effusion with punctate echo, and 1 case of effusion with flocculent echo; thickening and echo enhancement of soft tissue around the hip joint in 22 cases; unsmooth echo of articular cartilage of the femoral head in 9 cases; abnormal positional relationship between the femoral head and acetabulum in 5 cases (3 cases of hip joint instability and 2 cases of dislocation). Ten cases were treated conservatively and 12 cases received surgical treatment. Eighteen cases were cured. In the follow-up review, ultrasound showed 1 case of femoral head reduction, 2 cases of femoral head necrosis, and 1 case of heterotopic ossification.

The ultrasound findings of septic hip arthritis in neonates and infants are mainly joint cavity effusion with hip dislocation. Hip ultrasound is helpful for the diagnosis and follow-up of septic hip arthritis, which can improve the prognosis of children.