Background The ossific nucleus of the femoral head is usually present ultrasonographically around 12 weeks of age. It has been considered that the presence of an ossific nucleus in the femoral head is an indication of hip stability. In the ultrasound scan clinic for the assessment of developmental dysplasia of the hip at Sheffield Children’s Hospital, we have identified unstable hips with ossific nuclei, as well as, the appearance of ossific nuclei at as early as 2 weeks of age. These observations suggested the need to clarify the initial considerations that the ossific nucleus appeared ultrasonographically around 12 weeks of age and was an indicator of hip stability.

Aim To determine the relationship, if any, between the presence of the ossific nucleus of the femoral head ultrasonographically and stability of the hip.

Patient selection We have included in our study all the children who have had an ultrasound scan of their hips from 1996 to 1999 at Sheffield Children’s Hospital for suspected developmental dysplasia.

Methodology We have retrospectively reviewed reports of ultrasound scans performed for developmental dysplasia of the hip between 1996 and 1999. We have looked at the report for both the hips of each child. We have collected and analyzed data with regard to the age of the child at the time of the scan, the depth of the acetabulum, the shape of the femoral head, the presence or absence of an ossific nucleus, the dynamic stability of the hips and the congruity of the joint as reported on the ultrasound report. We report the findings in the first 318 hips of the 627 available patients in the study period.

Results The ossific nucleus can appear as early as 2 weeks and yet may not be visible until 24 weeks. In the 318 hips examined the ossific nucleus was present in 46 (14.47%). The age range for these scans was 1–40 weeks after birth. Of the 318 hips 252 (79.24%) were stable on dynamic screening, 274 (86.16%) had a normal(spherical) appearance of the femoral head, 209 (65.72%) had normal acetabular development and 263 (82.7%) demonstrated congruence of the hip joint. These data have been analyzed using Microsoft excel at confidence intervals of 0.8, which suggest no relationship between the presence of the ossific nucleus and hip stability.

Conclusion The limited early results of this study have shown that the ossific nucleus of the femoral head can appear from a very early age, may not appear until well after 12 weeks of age and is not an indicator of hip stability. Its presence on ultrasound scan does not exclude developmental dysplasia of the hip.