A 3-month-old female infant born to a primigravida mother presents to the pediatric clinic for routine developmental screening. The mother reports that the baby was in breech presentation at delivery. On examination, the pediatrician notes asymmetry of the gluteal and thigh skin folds, with the left side appearing lower than the right. Abduction of the left hip is restricted to 60 degrees. The Barlow test is positive on the left side. What is the most appropriate next step in management?