[The significance of the craniolateral acetabular margin for hip dysplasia evaluation]

The weight-bearing part of the canine hip is its dorsocraniolateral portion. On the radiograph the configuration of the craniolateral acetabular rim is important for evaluation of hip dysplasia. Changes in formation of this area should be differentiated from artefacts due to malpositioning. When the pelvis is tilted dorsally, the cranial acetabular rim is superimposed on the cranioventral acetabular contour and the acetabular roof. The craniolateral contour then seems to be missing. The contours of a ventrally tilted pelvis do not overlap, but it is difficult to discern the craniolateral rim. The reference points for Norberg-Olsson's measurements are difficult to choose in both cases and the angles may vary up to 10 degrees. A symmetrically positioned pelvis shows one point of reference for Norberg-Olsson's measurement where the cranial acetabular contour, the cranioventral margin and the acetabular roof intersect. Therefore poor positioning of the pelvis for radiographic evaluation of hip dysplasia should be avoided when using Norberg-Olsson's measurements.