Painful paediatric hip: frog-leg lateral view only!

For hip complaints in the paediatric population, it is common practice to acquire both anteroposterior (AP) and frog-leg lateral (FL) radiographs. This combination of views provides a high diagnostic yield, but also doubles radiation exposure. We investigated the diagnostic accuracy of obtaining a solitary FL view as compared to a combination of the AP and FL view.

Hip radiographs of 524 children (aged 2-15 years) referred for acute hip pain were retrospectively assessed by two independent radiologists. Cases of trauma, neuromuscular disorders or a history of known hip disease were excluded. Radiologists were blinded to the AP radiograph while assessing the solitary FL radiograph. We used Cohen's kappa test to calculate agreement between the assessment of both views and the solitary FL view.

Agreement between the assessment of the solitary FL view and the combination of the AP and FL view was very high with a kappa value of 0.989.

The diagnostic accuracy of the FL radiograph in cases of hip complaints in children is as high as the current standard employing both AP and FL views. Therefore a solitary FL radiograph appears sufficient. This practice would substantially reduce radiation exposure.

• Radiation exposure in children should be kept to a minimum. • In paediatric hip radiography a solitary frog-leg lateral view suffices. • This reduces radiation exposure and costs of imaging.