Ultrasound measurement and analysis of the hip in healthy infants: a multicenter study

Objective To analysis the change of hip joint in healthy infants by ultrasound, and establish the normal reference value of the developmental dysplasia of the hip(DDH). Methods A total of 8 000 healthy infants from 0 to 24 weeks were collected from the Multi-center study of 10 children′s medical centers. Among them, 3 855 infants(2 065 females and 1 790 males) with complete data and follow-up were included in this study. All subjects were divided into 6 groups (<4, 4~7, 8~11, 12~15, 16~19 and≥20 weeks group). α angle, femoral head length and width, femoral head coverage ratio by acetabulum (FHC) were measured in the coronal view on the neutral position; distance from pubis to femoral head (P-H) and distance from ischium to femoral head (I-H) were measured in the transverse view on neutral position; distance from femoral head topubis (H-P) was measured in the posterolateraltransverse view on the flexion position. The results of each group changes with age were analysised. Results ①The α angle of healthy infants from 0 to 20 weeks were increased with age, the difference among the groups were statistically significant(P 0.05). ②The femoral head length and width of all age groups were increased with age, the difference among all the groups was statistically significant(all P 0.05). ④The P-H and I-H in all age groups showed no statistically significant (all P>0.05). ⑤The H-P of all age groups were increased with age, the difference between the groups were statistically significant(all P<0.05). Conclusions The development of hip joints have the certain regular developmental pattern in healthy infants less than 5 months of birth and are relatively constant after birth more than 5 months. The ultrasound normal reference value of the hip joints can be used for the early diagnosis of the DDH. Clinical Trial Registry ChiCTR-ODC-16008748 Key words: Ultrasonography; Developmental dysplasia of the hip; Infant; Normal reference value