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Do Normal Early Ultrasound Findings Predict Normal Acetabular Development? A Study of Late-Presenting Dysplasia in
Jing Shi1, Yuchan Li2, Changhe Fan3
1Diagnostic Imaging Center, Shanghai Children's Medical Center, Shanghai Jiaotong University School of Medicine, Shanghai.
Background:
Developmental dysplasia of the hip (DDH) is increasingly recognized as a dynamic condition that may evolve after birth. This study aims to evaluate the natural history of hips with normal or borderline findings on early ultrasound and to identify imaging features associated with late-presenting acetabular dysplasia.
Methods:
We retrospectively reviewed the medical records of children who underwent hip ultrasonographic screening between March 2020 and February 2023. Children with Graf type I hips who had pelvic radiographs after 2 years of age were included. Graf type I hips were further subdivided into 4 subgroups according to the β angle (≤55 or >55 degrees) and the bony rim morphology (blunt or sharp). Acetabular index was measured and evaluated on the final follow-up pelvic radiographs, and acetabular dysplasia was defined as an AI >2 SDs above the mean.
Results:
A total of 87 children (174 hips) met the inclusion criteria. The mean age at the final ultrasound was 17.2±5.7 weeks, the mean α angle was 66.4±2.5 degrees, and the mean β angle was 52.9±4.0 degrees (range: 41.0 to 63.4 degrees). The mean age at the final radiographic follow-up was 2.9±0.6 years. Twenty-two hips were classified as acetabular dysplastic. There was a significant association between sex and acetabular dysplasia (χ2=7.19; P=0.007; OR=6.17; 95% CI: 1.39-27.38). A blunt bony rim on the final ultrasound examination was identified in 29 hips and was strongly associated with acetabular dysplasia (χ2=26.02; P<0.001; OR=9.53; 95% CI: 3.58-25.37).
Conclusions:
Graf type I hips with a blunt bony rim may not be entirely equivalent to mature, normal hips and may represent a subgroup susceptible to developing acetabular dysplasia during growth. Careful surveillance of hips with subtle morphologic abnormalities, particularly in female children, may therefore be warranted to facilitate early detection of acetabular dysplasia.
Level Of Evidence:
Retrospective level III.
