Reliability of MRI-based grading using Yoon's classification for labral tears in hip dysplasia

Labral tears in hip dysplasia arise from structural instability and excessive shear forces. Yoon's classification system, based on arthroscopic findings, was developed to reflect the natural course of labral tears in hip dysplasia and guide surgical decision-making. However, its reliability when applied to MRI-based grading remains unclear. We retrospectively included 105 hips from 88 patients with hip dysplasia, including borderline hip dysplasia, who underwent arthroscopic labral repair between 2022 and 2024. Labral tears were classified arthroscopically using Yoon's classification. MRI grading was independently performed by two observers. The reliability between MRI and arthroscopic grading was assessed using Cohen's weighted kappa and Gwet's Agreement Coefficient 1 (AC1); correlation was evaluated with Kendall's tau-b. Inter- and intra-observer reliabilities were also analysed. Most labral tears were arthroscopically graded as Grade 3 (81.0%) and primarily located in Zones 2-3 (79.0%). The reliability between MRI and arthroscopic grading was moderate (κ = 0.49 for observer 1, κ = 0.54 for observer 2). Inter-observer reliability was moderate (κ = 0.60), and intra-observer reliability was good (κ = 0.69) (P < .001). The observed percent agreement was 81.0% and Gwet's AC1 showed good reliability (0.782, P < .001). The reliability between MRI-based and arthroscopic grading was moderate according to Yoon's classification. Discrepancies, particularly in assessing CLR integrity, highlight the need to interpret MRI findings alongside clinical evaluation when planning treatment for labral tears in hip dysplasia.