Abstract: Objective:To verify the consistency of hip arthrography and magnetic resonance imaging(MRI) for evaluating acetabular bone and cartilage covering in children and to explore the advantages of intersection or complementarity between the two.Methods:Clinical data were retrospectively reviewed for 16 children with developmental dysplasia of the hip(DDH) undergoing at least one closed reduction and plaster fixation from November 2020 to November 2021 (2 cases underwent plaster fixation thrice, 4 cases twice, 10 cases once). There were 3 boys and 13 girls (8 bilateral, 8 unilateral; 6 left and 2 right). A total of 32 hip joints (24 affected, 8 normal) were measured.The average age of initial operation was (11.88±5.29)(4-22) months.Acetabular index(AI) and labrum AI were measured by intraoperative arthrography film and MRI within 2 days post-operation.According to the exclusion criteria, 40 data sets were finally acquired.They were divided into two groups of MRI and arthrography.Intra-class correlation coefficient(ICC) was utilized for evaluating the consistency of the same parameter.Pearson's correlation analysis was performed between AI and labral AI groups for clarifying the relationship between bony coverage and cartilage coverage.Results:ICC value of AI in MRI group and arthrography group was higher: 0.775(95% CI: 0.609-0.872); ICC value of labrum AI was moderate: 0.621(95% CI: 0.398-0.784). Pearson's correlation analysis revealed a positive correlation between AI and labrum AI on MRI ( r=0.591, P<0.001). Also a positive correlation existed between AI and labrum AI on arthrography film ( r=0.428, P<0.05). Conclusions:Regarding bone coverage index-AI and cartilage coverage index-labrum AI, average value of MRI is always slightly higher than that on arthrography film.However, the two have excellent consistency.It hints that hip arthrography and MRI have certain substitutability in measuring the same parameter.