Abstract
Background
Hip dysplasia has traditionally been classified based on the lateral center edge angle (LCEA). A recent meta-analysis demonstrated no definite consensus and a significant heterogeneity in LCEA values used in various studies to define hip dysplasia and borderline dysplasia. To overcome the shortcomings of classifying hip dysplasia based on just LCEA, a comprehensive classification for adult acetabular dysplasia (CCAD) was proposed to classify symptomatic hips into three discrete prototypical patterns of hip instability; lateral/global, anterior, or posterior. The purpose of this study was to assess the reliability of this recently published CCAD.
Methods
One hundred thirty-four consecutive hips that underwent a PAO were categorized using a validated software (Hip2Norm) into four categories of normal, lateral/global, anterior or posterior. Based on the prevalence of individual dysplasia and using KappaSize R package version 1.1, seventy-four cases were necessary for reliability analysis: 44 dysplastic and 30 normal hips were randomly selected. Five surgeons (3 fellowship trained in hip preservation) did a first reading (Time 1) to classify the hips, followed by four raters for a second reading (Time 2) minimum two weeks apart. Thereafter, a consensus meeting was held where a simplified flow diagram was devised before a third reading by four raters using a separate set of 74 radiographs took place.
Results
There was substantial and almost perfect intra-rater agreement for 4 surgeons between Time 1 and Time 2. At time 1 and time 2, there was substantial agreement overall between all surgeons; however, posterior and anterior rating categories had moderate and fair agreement at time 1 and time 2, respectively. At time 3, overall reliability and posterior and anterior rating improved from Time 1 and Time 2.
Conclusion
This comprehensive classification system provides a reliable way to identify three categories of acetabular dysplasia that are well-aligned with surgical management. The term borderline dysplasia should no longer be used.
