Influence of radiographic positioning in the interobserver measuring of the tibial plateau angle in dogs

ABSTRACT This work aimed at demonstrating that an inadequate radiographic position of pelvic limbs of dogs, from a strict lateral radiographic view, resulted in oblique images, affecting the measurement of the tibial plateau angle (TPA). There were two radiographic projections of the right and the left pelvic limb, one in strict lateral radiographic view and another with inclined hind limb in 21 dogs from the clinical surgical assistance at Hospital Veterinário of Universidade de Cuiabá in Cuiabá-MT. Inclusion criteria were dogs free from pelvic hind limbs orthopedic affection records, weighing between 15 and 40 kilos, without a preference for breed or gender and ageing between two and seven years old. A total of 42 radiographic images in strict lateral radiographic view and 42 inclined limb radiographic views were obtained. Three observers with TPA calculation experience made measurements. In the calculus for the strict lateral radiographic view the first observer has reached an average of 23,35º ± 2,82, the second observer 23,88º ± 4,83 and the third observer 24,54º ± 4,01. No significant statistic differences among the calculus of the three evaluators p=0,944 (P>0,05) was found. In the calculus of the inclined limbs radiographic views the first observer reached an average of 21,69º ± 4,22, the second observer 19,42º ± 5,92 and the third observer 22,64º ±. 5,23. Significant statistic difference in the calculus of the three observers, p=0,016, that is to say, P<0,05 was found. The data indicated that the inclined limb radiographic image compromises the final value of the calculation of tibial plateau angle in dogs. Thus, correct positioning of the pelvic limb, in a strict lateral radiographic view, must be always used for obtaining images aiming at measuring the value of TPA.