Pediatric hip (frog leg lateral view)

Last revised by Andrew Murphy on 23 Mar 2023

The frog leg lateral view is a special pelvis radiograph to evaluate the hip. Some departments will perform this routinely instead of the AP pelvis view to reduce exposure and maintain high diagnostic accuracy 1

The bilateral examination allows for better visualization of the hip joints and femoral neck. It is almost exclusively used in the pediatric population. It is an important view in the assessment of: 

  • the patient is supine with no rotation of the pelvis

  • the affected limb is flexed at the knee approximately 30° to 40°, and the hip is abducted 45° (this can be bilateral)

  • if unilateral, the heel of the affected limb should rest against the medial aspect of the contralateral knee

  • if it is a bilateral examination, both knees are to be resting on sponges, giving the appearances of "frog legs"

  • lateral projection

  • centering point: midway between the anterior superior iliac spine and the pubic symphysis

  • collimation

    • superior to the iliac crest

    • inferior to the proximal third of the femur

    • lateral to the skin margins

  • orientation: landscape

  • detector size: 24 x 30 cm or will vary depending on the patient's size

  • exposure 2

    • 63-70 kVp

    • 2-5 mAs

  • SID: 100 cm

  • grid: highly variable due to the view being a specialized pediatric projection

  • the entirety of the bony pelvis is imaged from the superior of the iliac crest to the proximal shaft of the femur

  • the obturator foramina appear equal

  • the iliac wings have an equal concavity

  • greater trochanters of the proximal femur are in profile

Preparing the room beforehand (setting up the detector, exposure and preparing lead gowns) is extremely beneficial for pelvis imaging, as young children will often begin to cry the moment they are placed supine.

Ideally, if a parent/carer holding is required, the parent holds the child from the foot-end in order to be in the child's direct line of sight. This is to avoid the child rotating their pelvis to look at their parent;

  • this will require clear instructions for the parents to follow so that they do not allow rotation of the child's pelvis or motion artifact from kicking

  • if the parent is accompanying the child by holding them in position, whilst the parent puts on a lead gown, it is the radiographer's responsibility to ensure the baby does not roll off the x-ray table

  • If the pediatric patient can be kept still using other methods such as distraction techniques, or swaddling, this is ideal to avoid scattered radiation to parents and staff 3

  • in some institutions, pediatric patients with hip pain may be assessed with a single frog leg view to reduce radiation exposure. This is evidence to support this approach, but individual practice will vary by department 5

Contact lead shielding is no longer recommended for any pediatric examination, multiple radiological societies have released statements supporting the cessation of this practice 9-12, the most comprehensive guidance statement on this matter (86 pages) is a joint report found at this citation 13.

Please see your local department protocols for further clarification as they may differ from these recommendations.

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Cases and figures

  • Case 1: normal frog leg lateral
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  • Case 2: normal frog leg lateral
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  • Case 3: left SUFE
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  • Case 4: left SUFE
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  • Case 5: Perthes disease
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