This paper begins by describing the parameters that potentially impact the quality of antero-posterior (AP) and lateral radiographs of the hip, and the variations in lateral radiographs that can be used. Radiographic examination remains the mainstay of the initial assessment however, common parameters are required to assist in the formation of accurate diagnoses and appropriate management plans including appropriate further imaging. When the patient is properly positioned, as in Figure 2D, it is evident that coverage of the dorsal acetabular rim (white arrows) is similar on both sides.An enhanced awareness of the presence of structural disorders of the hip, such as developmental dysplasia of the hip and femoroacetabular impingement (FAI), has fuelled an evolution in the assessment of patients with hip pain and enhanced our ability to diagnose patients, even in cases where there are mild structural abnormalities. The dorsal acetabular rim (white arrows) appears to provide more coverage of the right femoral head and less coverage on the left side. Oblique positioning will result in false assessment of dorsal acetabular rim coverage of the femoral head, as shown in Figure 2C. Additionally, the left (down) ilium appears narrower. In this image, the right (up) obturator foramen is increased in width compared with the left. In Figure 2B, the right hemipelvis has been elevated from the imaging plate. The pelvis is rotated with the right hemipelvis farther away from the imaging plate. The right stifle should be moved axially (medially) so the femurs are parallel. The right femur/stifle should be further internally rotated (so the patella is more centrally located over the femur). In this example, there are multiple positioning errors. Pelvic radiographs must be assessed for adequate positioning and should be repeated if the pelvis is oblique, as in Figure 2A. Ensuring that both limbs are positioned similarly allows side-to-side comparisons. This can be useful when radiographic changes are equivocal. Figure 1C shows an example of the pelvis correctly positioned.Īltering the degree of limb extension or flexion and changing the degree of internal or external rotation can significantly affect the appearance of the femoral head and neck. Ideally, the sacrum, ilial wings, and entire 7th lumbar vertebra should be included in the image. Note the uniform and equal size of the obturator foramen on this well-positioned radiograph. In this image the femurs are parallel with each other and parallel with the imaging plate. If the stifles are kept internally rotated, the patella should be centrally located over the distal femurs, as seen in the normally positioned radiograph ( Figure 1B). The limbs are then extended, maintaining the internal rotation, until the femurs are parallel with the table. While in a flexed position, the limbs are internally rotated and abducted so that the stifles are almost touching. All but the pelvis and hindlimbs are within the trough. This view is best obtained with the dog placed in dorsal recumbency, which is done by using a foam positioning trough. Step-by-Step: Pelvic Radiography Positioningįigure 1A demonstrates the normal positioning for the ventrodorsal hip-extended view (the view that should be submitted to the Orthopedic Foundation for Animals).