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→Measurements: Missing numbers
*(B) '''Perkin line''' is perpendicular to Hilgenreiner line, touching the lateral margin of the acetabulum. This leads to four quadrants and a normal femoral head has to be located in the inferomedial quadrant. We can measure the lateral displacement of the femoral head with regard to the Perkin line by dividing the width of the head that crosses the Perkin line by the diameter of the head. The value for patients under 3 years must be 0 and in older children this ranges from 0 to 22%.
*(C) '''Shenton line''' is a continuous arc drawn from the inner edge of the femoral neck to the superior margin of the obturator foramen. This should be smooth and undisrupted; otherwise it may indicate a fracture or hip dysplasia.
*(D) The '''acetabular index''' measures the acetabular roof slope. It is the most useful measure of acetabular dysplasia until 6 years of age. It is formed between Hilgenreiner line and the acetabular roof. In newborns, values of '''30° ±4° in males females''' and '''26° ±5° in females males''' are considered normal. Gradually this angle becomes smaller, with a mean value of '''20° ±3° in males females''' and '''18° ±4° in females males''' at 1 year of age.
*(E) The '''medial articular joint space''' is measured between the medial border of the femoral head or neck (when epiphysis is not ossified) and the acetabular platform. Normal values range between 5 and 12 mm. Differences greater than 1.5 mm between the two sides are considered abnormal.
