Reliability of radiological parameters measured on anteroposterior pelvis radiographs of patients with developmental dysplasia of the hip.

In order to evaluate the reliability of radiological parameters, we retrospectively reviewed the anteroposterior pelvic x-rays of 30 hips in 15 patients with developmental dysplasia of the hip. The following parameters were studied: acetabular index, center-edge angle, c/b ratio, Sharp's angle and teardrop figure. Each of the two authors measured the parameters twice on two separate days. Statistical assessment of the interobserver and intraobserver reliability was performed. The measurements of acetabular index and c/b ratio were reliable according to both intra- and interobserver reliability analysis, whereas center-edge angle, teardrop figure and Sharp's angle evaluations were reliable in the intraobserver comparisons but not in the interobserver comparisons. In conclusion, both acetabular index and c/b ratio may be used safely in the evaluation of developmental dysplasia of the hip.