Pediatric musculoskeletal disorders Quiz: Ace Your Exams

A 2-month-old girl is brought to the office for a routine newborn evaluation. She was born at 40 weeks gestation to a 28-year-old primigravid mother via cesarean section due to breech presentation. The remainder of the pregnancy and delivery were uncomplicated, and all prenatal tests were within normal limits. The infant breastfeeds every 4-5 hours and sleeps 7-8 hours at night. Physical examination shows an alert female infant with normal strength and movement in all extremities. There are four skin creases along the patient’s inner right thigh and two on the left thigh. Further examination reveals a limb length discrepancy of 1 inch. The physician gently adducts and applies pressure to the right hip which results in posterior displacement and a palpable clunk. Which of the following best describes the most likely etiology of this patient’s condition?