The normal width of anterior hip synovial recess in children.
To establish the diagnostic criteria for hip joint effusion, the normal width of the anterior hip synovial recess in children and the difference between both hips of the same child were examined in this study. Eight kindergarten schools were randomly selected for study in Kaohsiung City. The width of anterior hip synovial recess of 1,568 hips in 784 children (421 boys, 363 girls) was measured by ultrasound scanner with 7.5-MHz linear probe. The age of children ranged from 2.5 to 6.6 years old. During measurement, the children were put in supine position with hips and knees in extension and patella facing up. The results revealed that the mean width of the anterior synovial recess was 7.29+/-1.15 mm. Linear correlation of the width of synovial recess to age and height was disclosed and expressed as follows: width (millimeters) equal to 6.52+0.013x age (months), or width (millimeters) equal to 3.97+0.030x height (centimeters). The mean difference between both hips of the same child was 0.611+/-0.523 mm, and the difference was independent from the factors of age, gender, height, or weight (p>0.05). Ninety-five percent of the differences should be < or =1.46 mm, so that if the difference between hips is >1.46 mm, hip joint effusion should be suspected.