case_images: PMC9177065_01
case_images: Calculation of the Southwick angle in the "frog leg"
  incidence.
case_images: 1809-4406-aob-30-02-e245479-gf1.jpg
case_images: PMC9177065_01_1809-4406-aob-30-02-e245479-gf1.jpg
case_images: f1
case_images: Figure 1 shows the radiography of Patient 3, 11 years old, preoperative, Southwick angle: 81  (affected side, left) - 13  (unaffected side, right) = 68 .
case_images: Patient 3 of Figure 1, 12 years
  old, one year and two months after surgery.
case_images: 1809-4406-aob-30-02-e245479-gf2.jpg
case_images: PMC9177065_01_1809-4406-aob-30-02-e245479-gf2.jpg
case_images: f2
case_images: Alterations that are compatible with the various stages of osteonecrosis of the proximal femur on control radiographs (anteroposterior and profile) were analyzed, including: presence of cysts or sclerosis in the femoral head, presence of the crescent sign (subchondral fracture), and flattening or collapse of the femoral head (Figure 2). 