A retrospective study on isolated acetabular edge blunting in infants: clinical significance and proposed follow-up protocol.

BACKGROUND: Graf-based ultrasound (US) is widely used to screen for developmental dysplasia of the hip (DDH), a common orthopedic disorder, in infants. However, isolated acetabular edge blunting is occasionally reported, despite normal alpha and beta angles and adequate femoral head coverage. The clinical significance and follow-up strategies for this isolated finding remain unclear. In this study, we aimed to evaluate acetabular development in infants with isolated acetabular edge blunting and propose a rational follow-up protocol. METHODS: This retrospective study reviewed 5,190 reports on hip USs performed between June 2023 and July 2024. A total of 211 infants with isolated acetabular edge blunting and normal alpha-beta angles were included in this study. Demographic data, follow-up US results, and pelvic radiographs taken after 6 months were analyzed. Acetabular index (AI) angles and femoral head ossification center areas were measured and statistically compared. RESULTS: Of 211 infants, 144 (68.2%) were female. Spontaneous normalization to Graf type 1 A was observed in 58.7% of patients on the second US and 11.4% on the third US. At 6 months, pelvic radiographs were available for 37 infants, none of whom showed DDH according to the Tönnis classification. However, 54.0% had significantly higher AI angles on the blunting side than on the contralateral side (mean difference, 3.5°; p = 0.012). No significant difference was found in the femoral head ossification center area (p = 0.712). CONCLUSIONS: Isolated acetabular edge blunting does not progress to DDH but is associated with slightly higher AI values, suggesting subtle variations in acetabular development. In follow-up protocols, a second US and follow-up with a pelvic radiograph at 6 months is sufficient instead of unnecessary repeated ultrasonography checks. Larger prospective studies are required to clarify the long-term clinical significance of these findings.