Developmental Hip Dysplasia Diagnosis at Three-dimensional US: A Multicenter Study

Normal variation of infant hip development

“…We semi-automatically measured conventional DDH indices (α angle and FHC) on the manually identified Graf’s SP. We also measured new 2D and 3D indices developed by Hareendranathan at al, 19 Mabee et al, 16 and Zonoobi et al 14 on the slices containing acetabulum. While indices measured on the single Graf’s SP slice and across whole acetabulum are referred to with subscript “SP” and “Total”, respectively; indices measured across the acetabular slices located anterior and posterior to the Graf’s SP use subscript “Ant” and “Post”, respectively ( Table I ).…”

“…ACA is measured as the angle between the summed point normals for the iliac wing surface and acetabular roof surface. 14 , 16 , 17 Mabee et al 16 reported significantly higher reliability and slightly higher diagnostic accuracy of ACA when compared to the conventional α angle. Apart from angularity, roundness of the acetabulum is considered during hip examination in most centres.…”

“…11 , 13 Secondly, a 2D image ignores structural variations present in anterior and posterior regions. Earlier works have shown that 3D ultrasound (3DUS) provides a better interpretation of all regions of the hip joint, 12 reduces follow-ups, 14 and is easier to acquire for novice sonographers. 13 Various 2D and 3D indices of α angle, FHC, acetabular contact angle (ACA) and osculating circle radius (OCR), have been developed to aid interpretation of 3DUS ( Figure 1 ).…”

“…OCR is the radius of the circle best fitting under the apex of the acetabular curve ( Figure 1 ) and is generally larger in more rounded (more dysplastic) hips. 14 , 19 While OCR indices are not independent diagnostic indices of DDH, they may supplement angularity measures (like α angle and ACA indices) to resolve cases in the ‘borderline’ category.…”