Fig. 4

a Preoperative pelvic anteroposterior view in a 17-month-old girl on left hip dislocation with the modified Smith–Petersen approach. b, d–f Radiograph at 32, 64, 90, and 103 months after open reduction, respectively, without obvious AVN sign. f demonstrates suspicious early signs of type 2 AVN such as slightly laterally inclined proximally convex physis, medial femoral head flattening and an oval-shaped epiphysis. c MRI assessment at 32 months after open reduction