The Limping Teenager

Hint

If a SUFE is suspected, then an anterior-posterior view of the pelvis and a frog lateral view radiograph of both hips is required and is the most appropriate answer.

One would look for Trethowan’s sign: where a line, known as Kline’s line is drawn along the femoral neck on an anterio-posterior radiograph and should pass through the lateral margin of the femoral head. If the upper femoral epiphysis has slipped the line does not. This is best illustrated by the x-ray (figure1) in this case report summary.²

Aspiration of a joint is the investigation if an infected joint is suspected. Similarly, one may also wish to perform blood tests to confirm or rule out an infection, which is not the suspicion here.
An MRI of the hip may be helpful further down the line to confirm the diagnosis; but would not be an appropriate first line investigation.

Radiography: Anterior-posterior view of pelvis and lateral x-ray of left hip is what is performed in adults when suspecting a neck of femur fracture of a particular hip. In paediatric patients, it is important that both hips are imaged as both hips can be affected, and may not be symptomatic.