Correlation between sex, intrauterine position and familial predisposition and neonatal hip ultrasound results

Aim: To correlate findings of hip ultrasound on day 4 - 10 of life with sex, intrauterine position and a positive family history for congenital hip anomalies. Methods: The SNiP-study (Survey of Neonates in Pommerania) registered 2256 neonates (2030 term, 226 preterm) between May 2002 and March 2004. Hip ultrasound results of 1043 term and since October 2003 33 preterm neonates were analysed. Time of ultrasound was day 4 - 10 after birth. Preterm neonates were examined when reaching their corrected term gestational age. Ultrasound was applied with a 7.5 MHz linear scanner and results were classified according to Graf. Chi-square and Fishers exact test were used for statistical analysis. Results: 4.9% of the screened hips were classified as IIc or higher, 3.1% were unilateral and 1.7% bilateral. Incidence was significantly higher (p < 0.023) in females (6.6%) than in males (3.2%). There was no significant difference in intrauterine position or positive family history for hip anomalies with 3.7% for mothers, 1.2% of fathers and 2.4% of siblings positive. There was a higher incidence for congenital hip dysplasia in preterms with 6.1%, which is not significant due to the limited number. Discussion: Current screening methods miss up to 18% of newborns with severe hip dysplasia. We were able to demonstrate that screening for congenital hip dysplasia with ultrasound is a diagnostic tool even during the first days of life. There is a significantly higher incidence of congenital hip dysplasia in females, but in contrast to other studies we found no significant difference in intrauterine position or familial history. Earlier diagnosis and therapy on the base of relevant risk factors might correspond with an improved prognosis and outcome. Further studies are warranted to evaluate the significance in preterm neonates.