Comparison of morphologic and dynamic US methods in examination of the newborn hip.

PURPOSE

Comparison of morphologic and dynamic methods of hip ultrasonography (US) to differentiate normal from abnormal findings in the diagnosis of developmental dysplasia of the hip (DDH).

MATERIALS AND METHODS

A total of 6,800 hips in 3,400 infants were examined with US, using the morphological method of Graf, and the dynamic method of Harcke.

RESULTS

According to the Graf classification 81.47% of infants had Type 1 (normal hip), 10% Type 2a (physiologic immaturity), 2.44% Type 2b (acetabular dysplasia), 1.05% Type 2c (critical zone hip), 2.89% Type 3 (mildly dislocated), and 2.10% had Type 4 (dislocated) hips. Study in the transverse/neutral plane showed a normal relationship between the femoral head and the acetabulum in the 6,460 hips that were classified as Type 1-2c, that the hip was subluxated in 197 hips of Type 3, and was luxated in 143 hips of Type 4. Dynamic study with stress maneuver of the Type 1-2a hips showed that while 91.48% of the Type 1 hips (n = 5540) were stable and 8.52% were unstable, 92.37% of the Type 2a hips (n = 682) were stable and 7.63% were unstable. Dynamic study was not performed in cases that were diagnosed as Type 2b or worse. Follow-up US showed progression from Type 2a to Type 2b in 2.63% of Type 2a cases. Of the cases, 1.7% that were morphologically normal (Type 1) but unstable in their initial US examination, were revealed to be Type 3 later in the repeat US examination.

CONCLUSION

We believe that overtreatment and delayed treatment rates of DDH will be minimized by the use of both morphological and dynamic US methods in the evaluation of the newborn hip.