A 4-month-old infant with developmental dysplasia of the hip (DDH) is treated with Pavlik harness. After 3 months, hips remain unstable despite compliance. What is the next best step?

Correct option is C

If Pavlik harness fails by 3–6 months, the next step is closed reduction under anesthesia with hip spica application. Open surgery is reserved for older children.
Explanation of options: (a) ✘ Continuing ineffective harness delays definitive correction. (b) ✘ Rigid brace is not effective after Pavlik failure. (c) ✔ Correct; closed reduction + spica is standard after failed harness. (d) ✘ Open reduction is reserved after 18 months age or failed closed reduction.