Anatomical insights beyond the center edge angle in Borderline Hip Dysplasia: A Computerized tomography study

BackgroundBorderline hip dysplasia (BhD) might be associated with insufficient acetabular coverage. Thus, we investigated potential differences in acetabular anatomical measurements derived from computerized tomography (CT) that characterize BhD compared with healthy controls. MethodsBhD patients (LCEA between 18{o} and 25{o}) and healthy controls (LCEA between 25{o} and 40{o}) underwent anteroposterior pelvic X-ray and CT to study Wiberg and Tonnis angle, extrusion and Fear index, notch width and depth, anterior and posterior wall height, anterior and posterior articular surfaces, articular circumference, the ratio between the anterior articular surface and the articular circumference, the ratio between the posterior articular surface and the articular circumference, and the ratio between the notch width and the articular circumference. An independent two-tailed t-test, U of Mann-Whitney test, and odds ratios were obtained ( = 5%). ResultsTwenty-three BhD patients aged 31.5 {+/-} 8.3 years and LCEA 21.6{degrees} {+/-} 4.0{degrees} and thirty-one healthy controls aged 34.1 {+/-} 8.0 years and LCEA 33.7{degrees} {+/-} 5.5{degrees} were included. The sensitive CT features for BhD were anterior (p < 0.001) acetabular surface, anterior (p = 0.009), anteroposterior (p = 0.008) and posterior (p < 0.008) acetabular surface ratios, and acetabular notch width (p = 0.002). ConclusionsBhD CT characterization provides tridimensional anatomical insights beyond the LCEA. BhD insufficient acetabular coverage can be found along the superior (lower Wiberg angle, and increased Tonnis angle and extrusion index), anterior (lower anterior acetabular surface and anteroposterior acetabular surface ratio, and increased posterior acetabular ratio), and inferior (increased acetabular notch width) axis.