Normal radiographic parameters in paediatric pelvic radiographs from a Chinese population

Paediatric pelvic and hip radiographs are a common investigation used when assessing a child for suspected developmental dysplasia of the hip. This report describes an attempt to establish normal values of medial joint space, acetabular index and centre edge angle according to specific age groups and sex in a Chinese population. Patients who had undergone a pelvic radiograph as part of their assessment, but were subsequently found to have normal hips were recruited retrospectively. These patients were grouped according to sex and age; medial joint space, acetabular index and centre edge angle were measured in all radiographs. A mean±SD was calculated for each group, and then each age group was tested for statistical significance between the male and the female groups. A total of, 98 patients were recruited, who underwent 188 pelvic radiographs, resulting in images of 376 'normal' hips. The results for medial joint space, acetabular index and centre edge angle for each age and sex group are described. Only the acetabular index requires different reference ranges for male and female patients because of consistent statistical significance between the two groups. It was found that medial joint space remained fairly constant throughout the age groups, whereas the acetabular index decreased and the centre edge angle increased slightly. The reference ranges for the parameters described here are quite different from those established previously in a population of Northern-European descent, which could be because of a variety of reasons including genetics, body habitus and measurement technique. We believe that it would be prudent to implement these different ranges when assessing patients of Chinese heritage to optimize care of patients who may suffer as a consequence of not receiving treatment for missed hip dysplasia.

Diagnostic Study Level III - Study of nonconsecutive patients (without consistently applying the reference 'gold' standard).