Ultrasonographic Graf type IIa hip needs more consideration in newborn girls

According to hip ultrasonography by Graf's method, the type IIa hip has a certain degree of physiological delay in ossification of the bony acetabular roof. The aim of this case-control study was to evaluate the natural history of the type IIa hip.

Four hundred and thirty-one type IIa hips were identified in 312 of 1,690 ultrasonographically screened newborns with a mean age of 27 days. Parents were accurately informed about the prognosis of such a hip condition and invited for ultrasonographic re-examination at 6-7 weeks of age.

Type IIa hip was more common in newborn girls than in boys (P < 0.001). Among 431 type IIa hips, 146 (34 %) missed the follow-up examination at 6-7 weeks of age. Among the completely followed 285 hips, 225 (79 %) developed into a normal hip at 6-7 weeks of age. Newborn boys' hips had a higher rate of spontaneous normalization than girls' hips at 6-7 weeks of age (P = 0.006). All but one type IIa(+) hip became type I without any treatment. According to our management protocol, 35 type IIa(-) hips and one type IIa(+) hip, which later became type IIb, underwent treatment. The rate of treatment was higher in newborn girls' hips than in boys' hips (P = 0.019).

As Graf type IIa hip is more common, has a lower rate of spontaneous normalization and higher rate of treatment in newborn girls than in boys, we recommend paying more attention the type IIa hip in newborn girls. The rate of missing the required follow-up is unacceptably high due to parents' insensitivity regarding the type IIa hip.