DDH Follow-Up After 6 Months: Why Order X-Rays Later If Ultrasound Has Normalized?
Methods: We reviewed a consecutive series of infants with DDH presenting to our institution between January 2008 and January 2012. Infants less than 6 months of age with a previous DDH diagnosis were considered to have normalized DDH if their clinical exam and static/dynamic ultrasound revealed no signs of hip instability or acetabular dysplasia. We excluded infants with abnormal ultrasonographic indices and/or clinical exam, or those who required more invasive procedures to achieve hip stability at 6 months of age. Follow-up anteroposterior (AP) pelvic radiographs at approximately 6 months and 1 year of age were evaluated for evidence of residual acetabular dysplasia, defined as an abnormal acetabular index for age – greater than 30 degrees on the 6-month radiograph and greater than 28 degrees on the 12-month radiograph.
Results: Our study cohort consisted of 115 patients with normal sonographic and clinical exams before 6 months of age. At a mean age of 6.6 ± 0.8 months, 17% of all patients demonstrated signs of acetabular dysplasia on follow-up radiographs. Dysplasia was found in 13% of patients (10 of 79) with prior Pavlik harness treatment (PH) and 25% of patients (9 of 36) with risk factors for DDH (female gender, breech presentation, and/or positive family history) but no previous treatment with a Pavlik harness (RF). Patients who were not braced at this visit (n=106) were subsequently followed with an AP pelvic radiograph at an average age of 12.5 ± 1.2 months. The overall prevalence of acetabular dysplasia increased to 33%, including 34% of PH patients (25 of 74) and 31% of RF patients (10 of 32).
Conclusion: We were wrong. At 12 months of age, 33% of infants with previously normal clinical and sonographic examinations before 6 months of age had residual acetabular dysplasia. Longitudinal radiographic follow-up through at least 1 year of age is important to allow timely intervention and avoidance of future complications of residual dysplasia with increasing patient age.