How many degrees should the feet and lower limbs be internally rotated for an AP pelvis radiograph?

Citation, DOI & article data

Citation:

Murphy, A., Knipe, H. Pelvis (AP view). Reference article, Radiopaedia.org. (accessed on 08 Sep 2022) https://doi.org/10.53347/rID-44863

The AP pelvis view is part of a pelvic series examining the iliac crest, sacrum, proximal femur, pubis, ischium and the great pelvic ring. 

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This view is of considerable importance in the management of severely injured patients presenting to emergency departments 1. It helps to assess joint dislocations and fractures (i.e. iliopectineal line, ilioischial line, Shenton line) in the trauma setting, as well as, bone lesions and degenerative diseases. A properly aligned AP pelvis view is imperative in the assessment of early hip degeneration, in particular for the assessment of femoroacetabular impingement (FAI) and hip dysplasia 3. 

• patient is supine or standing 2,3
• lower limbs are internally rotated 15-25° from the hip (do not attempt this if a fracture is suspected) to demonstrate an AP view of the proximal femur

• AP projection
• centering point
  • the midpoint of the anterior superior iliac spine and the pubic symphysis 
• collimation
  • laterally to the skin margins
  • superior to above the iliac crests
  • inferior to the proximal third of the femur
• orientation  
  • landscape 
• detector size
  • 35 cm x 43 cm
• exposure
  • 70-80 kVp
  • 20-30 mAs
• SID
  • 100 cm 2 or 120 cm 3
• grid
  • yes

• entirety of the bony pelvis is imaged from superior of the iliac crest to the proximal shaft of the femur 2
• obturator foramina and acetabular teardrops appear symmetrical and midsacral line aligns with the pubic symphysis 2,3 
• iliac wings have an equal concavity 2
• greater trochanters of the proximal femur are in profile and the lesser trochanters are partially superimposed over the femoral neck 2,3
• sacrococcygeal joint 1-3 cm superior to the upper surface of the pubic symphysis 3

• internal rotation can be assisted with the use of sandbags over the lateral edges of the patient's feet
• if one obturator foramina appear ‘closed’, the patient could be rotated away from the image receptor on that side

References

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