Ultrasound Is an Alternative to X-ray for Diagnosing Developmental Dysplasia of the Hips in 6-Month-Old Children.

BACKGROUND

Infants previously treated for developmental dysplasia of the hips (DDH) are routinely imaged with ultrasound initially and reimaged with an anteroposterior (AP) pelvis X-ray at 6 months of age to assess for dysplasia. It has become convention to transition from ultrasound to AP X-ray at 6 months of age, but no study has demonstrated that ultrasound is inadequate at this age.

QUESTION/PURPOSE: The purpose of this study was to confirm that ultrasound for the 6-month DDH evaluation is a feasible alternative to the standard X-ray.

PATIENTS AND METHODS

Thirty-one 5- to 7-month-old infants undergoing AP pelvis X-ray related to previous Pavlik harness treatment for DDH or to a history of breech presentation were prospectively enrolled. All patients were imaged with an AP pelvis X-ray and bilateral hip ultrasounds. Three senior orthopedic surgeons unfamiliar with the patient histories evaluated both types of imaging for standard measures of hip dysplasia, including acetabular index (AI), alpha angle, and bony rim percent coverage of the femoral head. Pearson correlation coefficients were calculated for the X-ray and ultrasound measures.

RESULTS

Good quality ultrasound images were obtained in all patients, despite the presence of the ossific nucleus in 66% of the hips. All three reviewers correctly diagnosed the one dislocated hip via both X-ray and ultrasound. There were no false negatives on ultrasound, and none of the patients with negative ultrasounds required treatment during the mean 26 months of follow up. An increased AI on X-ray was correlated with lower percent coverage of the femoral head on ultrasound.

CONCLUSIONS

Ultrasound is a technically feasible DDH imaging modality that can be used as an alternative to X-ray for 6-month-olds.