A previous study demonstrated that the reproducibility of the Crowe (Cr), the Hartofilakidis (Ha) and the modified Cochin (Co) classifications were comparable. However, there were differences with a trend that suggested the influence of experience. Therefore, we performed a prospective study to investigate whether experience influenced the reproducibility of the commonly used developmental dysplasia of the hip (DDH) classifications.

The hypothesis was that the intra- and inter-observer reproducibility scores would be higher in the senior group than the junior group, and particularly for the modified Co classification.

Four seniors and four residents classified 104 A/P pelvic radiographs (200 hips) two times using the Cr, Ha and Co classification systems.

For intra-observer reproducibility, the average weighted concordance coefficients [95% confidence intervals] were for the senior and the junior groups: 92.2 [88.6–95.7] and 92.6 [87.9–97.2] for Cr, 92.1 [88.7–94.6] and 92.0 [87.7–96.3] for Ha, 94.2 [91.8–96.6] and 94.1 [91.5–96.6] for Co. The average weighted Kappa (95% confidence intervals) were 0.8 [0.71–0.88] and 0.79 [0.68–0.89] for Cr, 0.77 [0.74–0.81] and 0.75 [0.62–0.88] for Ha, 0.82 [0.76–0.89] and 0.80 [0.74–0.87] for Co. The junior inter-observer reproducibility multi-rater Kappa (list A:list B) were 0.57:0.50 (Cr), 0.47:0.53 (Ha), 0.42:0.42 (Co). Senior multi-rater Kappa were 0.53:0.49 (Cr), 0.40:0.34 (Ha), 0.40:0.43 (Co).

Contrary to our hypothesis, the experience of the observer did not affect the intra- and inter-observer reproducibility of the three classification systems.