Fig 1.
Flow chart of the study inclusion.
Fig 2.
Femoral head position: Concentric reduction vs. eccentric reduction.
A. Medial joint space distance is defined as the distance between the triradiate cartilage and femoral capital epiphysis. If the medial joint space width is 3 mm or less, it is defined as a concentric reduction. B. Eccentric reduction of the left DDH in a 17-month-old girl. Medial joint space distance is 6 mm. Note the dysplastic left acetabulum and no visible ossification center of the left proximal femoral epiphysis.
Fig 3.
Obstacles of closed reduction: MR features.
A. The contrast-enhanced axial T1-weighted image shows the pulvinar (asterix) as a thick fibrofatty tissue blocking concentric reduction in the left hip joint space. Note the punctate enhancement of the left proximal femoral epiphysis. B. Coronal T2-weighted with fat-suppression obtained after closed reduction of the left hip shows triangular shaped, hyperintense soft tissue at the chondrolabral junction of the left acetabulum (arrow) reflecting the neolimbus.
Fig 4.
Abduction angle measurement on MRI.
Abduction angle is measured on the MEDIC image. Hip abduction angle is defined as the angle between the line along the mid-femoral shaft and the line connecting the posterior end of the ischial tuberosities (α angle).
Fig 5.
Pattern of contrast enhancement of the proximal femoral epiphysis.
A. Contrast-enhanced coronal T1-weighted image in a 5-month old girl after closed reduction of the left hip shows a normal striated pattern of enhancement in the cartilaginous femoral epiphysis. B. Contrast-enhanced coronal T1-weighted image in a 4-month-old girl after closed reduction of the left hip shows a geographic area of decreased enhancement in the left femoral head. C. Contrast-enhanced axial T1-weighted image in a 7-month-old girl after closed reduction of the right hip shows a global decreased enhancement of the right femoral head.
Table 1.
Risk factors of AVN: Clinical features.
Fig 6.
Contrast enhancement of the proximal femoral epiphysis and development of AVN after closed reduction of DDH.
A. Contrast-enhanced axial T1-weighted image of a 7-month-old girl after closed reduction of the left hip shows a global decreased enhancement of the left proximal femoral epiphysis. Note the pulvinar in the left hip joint. B. Follow-up radiograph obtained 1 year after closed reduction shows a small, fragmented secondary ossification center of the proximal femoral epiphysis and widening of the femoral neck suggesting AVN.
Table 2.
Risk factors of AVN: MRI features.
Table 3.
Multiple regression analysis of risk factors of AVN.