Review Question - QID 3610

Initial ultrasound is performed to confirm reduction of the hip in question (generally after 1 or 2 weeks) followed by repeat ultrasound 6 weeks later. Ultrasound is necessary to avoid leaving an infant in a harness with an unreduced hip which can erode the acetabulum.

Weinstein et al. provide a thorough overview of the presentation, evaluation, and treatment of DDH. The use of office-based ultrasound has helped to confirm hip reduction and proper acetabular development in children being treated with Pavlik harness.

Swaroop and Mubarak performed a retrospective, comparative study looking at children with Ortolani-positive hips who were treated with either Pavlik Harness and education or with Pavlik Harness, serial ultrasound exams, and a hip abduction orthosis upon failure of Pavlik harness. They achieved 93% success in the latter group.

Illustration A shows an illustration of a neonatal hip ultrasound looks like. The alpha angle is illustrated by the blue line which should be greater than 60 degrees in a normal hip. Illustration B demonstrates an ultrasound of a dysplastic hip showing a rounded corner on the lateral acetabular edge (arrow) and a subluxated femoral head. The alpha angle in this hip is approximately 45 degrees. Illustration C demonstrates an ultrasound of a normal hip. Notice the sharp, lateral acetabular edge (arrow) which is consistent with normal hip development and the well-reduced femoral head. The alpha angle here is closer to 65 degrees. Illustration D shows an AP pelvis radiograph showing asymmetric ossification of the proximal femoral epiphysis. An asymmetric lack of ossification (as seen on the left side) should raise suspicion for hip dysplasia.

Incorrect Answers:
Answer 1: MRI requires sedation in patients of this age and is not required as ultrasound can provide the needed information. MR can be useful in confirming closed reduction in older children (6-12 months).
Answer 2: CT exposes the child to unnecessary radiation and is not needed to confirm hip reduction in the harness. CT can be useful in confirming closed reduction in a spica cast.
Answer 4: Plain radiographs can help make the diagnosis of hip dysplasia however they do not provide as much information as ultrasound imaging as the femoral head is not yet ossified in infants.
Answer 5: Arthrogram and fluoroscopy require sedation as well and are more appropriate if a closed reduction in the operating room is required.