Comparing Norberg angle, linear femoral overlap and surface femoral overlap in radiographic assessment of the canine hip joint.

OBJECTIVES:
The aim of this study was to compare Norberg angle, linear femoral overlap and surface femoral overlap in radiographs of hips accepted for official hip dysplasia screening.
METHODS:
Radiographs of 100 dogs (200 hips) were reviewed. The three measurements were performed in each hip according to previously described methods and thereafter correlated.
RESULTS:
Intra- and inter-observer reliability was very high (all >85%). The linear correlation between Norberg angle and linear femoral overlap or surface femoral overlap was 0·40 and 0·41, respectively. The linear correlation between linear femoral overlap and surface femoral overlap was 0·84.
CLINICAL SIGNIFICANCE:
Norberg angle cannot be compared with surface femoral overlap or linear femoral overlap, and a mathematical formula could not be computed for the comparison.