Radiographic Follow-up of DDH in Infants: Are X-rays Necessary After a Normalized Ultrasound?

BACKGROUND

Concerns about radiation exposure have created a controversy over long-term radiographic follow-up of developmental dysplasia of the hip (DDH) in infants who achieve normal clinical and ultrasonographic examinations. The purpose of this study was to assess the importance of continued radiographic monitoring by contrasting the incidence of residual radiographic dysplasia to the risks of radiation exposure.

METHODS

We reviewed a consecutive series of infants with idiopathic DDH presenting to our institution over 4 years. Infants with "normalized DDH" had achieved a stable clinical examination with an ultrasound revealing no signs of either hip instability or acetabular dysplasia. We excluded infants with persistently abnormal ultrasonographic indices, clinical examinations, or both by 6 months of age, including those requiring surgical reduction. Anteroposterior pelvic radiographs at approximately 6 and 12 months of age were then evaluated for evidence of residual radiographic acetabular dysplasia. Radiation effective dose was calculated using PCXMC software.

RESULTS

We identified 115 infants with DDH who had achieved both normal ultrasonographic and clinical examinations at 3.1±1.1 months of age. At the age of 6.6±0.8 months, 17% of all infants demonstrated radiographic signs of acetabular dysplasia. Of infants left untreated (n=106), 33% had dysplasia on subsequent radiographs at 12.5±1.2 months of age. No significant differences were evident in either the 6- or 12-month rates of dysplasia between infants successfully treated with a Pavlik harness and infants normalizing without treatment but with a history of risk factors (P>0.05). The radiation effective dose was <0.01 mSv for the combined 6- and 12-month single-view anteroposterior radiographs of the pelvis.

CONCLUSIONS

The notable incidences of radiographic dysplasia after previous DDH normalization in our study cohort appear to outweigh the risks of radiation exposure. Our findings may warrant radiographic follow-up in this population of infants through at least walking age to allow timely diagnosis and early intervention of residual acetabular dysplasia.

LEVEL OF EVIDENCE: Level IV-retrospective case series.