A 2-week-old female infant is brought to the pediatrician for her first newborn follow-up. She was born at term via elective cesarean section due to breech presentation. There were no complications during delivery. On physical examination, the clinician notes that the skin folds on the infant's thighs are asymmetric. When the clinician flexes the infant's hips and knees to 90 degrees and gently abducts the hips, a palpable clunk is felt on the left side. The right hip moves smoothly.
Which of the following is the most appropriate next step in the management of this patient?
The correct answer is:
E) Ultrasonography of the hips
The patient is presenting with developmental dysplasia of the hip (DDH), a condition where the femoral head has an abnormal relationship with the acetabulum. This patient has two major risk factors: female sex and breech presentation. The palpable clunk during abduction is a positive Ortolani maneuver, indicating that a dislocated femoral head has been reduced back into the acetabulum. In an infant younger than 4–6 months of age, the femoral head and acetabulum are primarily cartilaginous and are not well-visualized on plain X-rays. Therefore, ultrasonography is the gold-standard imaging modality for diagnosis and for guiding treatment in this age group.
Answer choice A: Follow-up in 2 months, is incorrect. DDH requires prompt intervention to ensure the acetabulum develops correctly around the femoral head. Delaying diagnosis can lead to permanent gait abnormalities and early-onset hip osteoarthritis.
Answer choice B: Immediate application of a Pavlik harness, is incorrect. While the Pavlik harness is the treatment of choice for DDH in infants under 6 months of age, ultrasound should be performed first to confirm the diagnosis and document the degree of dysplasia or dislocation before initiating treatment.
Answer choice C: Pelvic X-rays, is incorrect. X-rays are unreliable in infants under 4 months of age because the capital femoral epiphysis has not yet ossified. X-rays become the preferred imaging modality only after 4–6 months of age.
Answer choice D: Reassurance, is incorrect. While asymmetric skin folds can be seen in healthy infants, when combined with a positive Ortolani maneuver and a history of breech positioning, they are a significant clinical marker for DDH that must be investigated.
Key Learning Point
Developmental dysplasia of the hip (DDH) is most common in first-born females born in the breech position. Physical exam findings include positive Barlow (dislocatable) or Ortolani (reducible) signs and asymmetric skin folds. Ultrasonography is the diagnostic study of choice for infants <4–6 months of age. X-ray is used for older infants. Treatment is typically a Pavlik harness, which maintains the hip in flexion and abduction.
