Fovea alta on MR images: is it a marker of hip dysplasia in young adults?

Abstract

The objective of our study was to investigate the association between high fovea capitis (fovea alta) and hip dysplasia in young adults. In a retrospective study, blinded observers reviewed 82 pelvic radiographic and hip MRI studies of three groups of patients: those with developmental dysplasia of the hip (DDH) (center-edge angle, ≤20°), those with borderline DDH (center-edge angle, 21°-25°), and control patients (center-edge angle, >25°). The center-edge angle and coxa valga (femoral neck-shaft angle, >135°) were assessed on pelvic radiographs, and fovea alta was assessed on MR images (delta angle, ≤10°). The Mann-Whitney and Fisher exact tests were used to correlate fovea alta with DDH and with coxa valga, respectively. Interobserver agreement for center-edge and delta angles and the diagnostic performance of fovea alta as a marker of DDH were calculated. Thirty-one patients with DDH, 23 with borderline DDH, and 28 without DDH were included. Excellent interobserver agreement was found for center-edge angle (concordance correlation coefficient, 0.94) and for delta angle (concordance correlation coefficient, 0.91). Fovea alta had a significant association with DDH (p<0.001) but no association with coxa valga (p>0.57). A significant difference (p<0.001) was found between patients with DDH (3.4°) and those without DDH (21.7°) with respect to mean delta angle measurements. Fovea alta had 69.4% sensitivity, 82.1% specificity, 67.2% positive predictive value, 81.0% negative predictive value, and 75.6% overall accuracy as an indicator of DDH. Fovea alta shows promise as a strong MRI marker of DDH.