NEW YORK (Reuters Health) – In a study of newborns with dysplastic and potentially unstable hips, researchers found no difference in radiographic outcome at age 6 between children randomly assigned to immediate abduction splinting or active sonographic surveillance.

Both groups had radiographically normal hips at age six with no evidence of avascular necrosis, Dr. Karen Rosendahl of Haukeland University Hospital, Bergen, Norway and colleagues report in the March issue of Pediatrics, available online now.

Between 1997 and 2003, Dr. Rosendahl and her associates randomized 128 newborns with mildly dysplastic and potentially unstable hips (sonographic inclination angle of 43 to 49 degrees) to abduction splinting (with splinting discontinued when indicated by improvement) or active sonographic surveillance (with splinting when deemed necessary).

They previously reported that active surveillance halved the number of children requiring treatment (47% vs 100% in the immediate splinting group), did not increase the duration of treatment, and yielded similar results at 1-year follow-up.

However, 19 participants (30%) in the treatment group and 20 (31%) in the early surveillance group had radiologic evidence of delayed ossification, and 7 and 4, respectively, had at least 1 dysplastic hip at 1 year of age. None of the subjects’ hips were subluxed or dislocated.

They now report 6-year follow-up data, with respect to acetabular development and risk of avascular necrosis, on 83 of the original participants (42 from the immediate splinting group and 41 from the early surveillance group).

According to the investigators, the delayed acetabular ossification or persistent dysplasia seen in a third of infants from both groups at 1 year had completely resolved in all but 1 of the female subjects from the treatment group.

“Moreover, none of the hips showed any features suggestive of avascular necrosis,” they note. “This is an important observation because even small, partial avascular necroses may results in femoral head or neck deformities or growth disturbances typically presenting around puberty,” they point out.

In this context, the 6-year followup time period is short, they admit. However, they say the markers for avascular necrosis used in the study would disclose deformities of the femoral head and growth plate, as well as some of the known femoral neck deformities associated with an undergone avascular necrosis.

Pediatrics 2011;127:e655-e660. Published online March, 2011.