Accuracy of Caudocranial Canine Femoral Radiographs Compared to Computed Tomography Multiplanar Reconstructions for Measurement of Anatomic Lateral Distal Femoral Angle.

Abstract

This study aimed to compare the accuracy of sternal recumbency caudocranially obtained radiographs of canine femora to computed tomographic (CT) frontal plane reconstructions of the same femora for assessing anatomic distal lateral femoral angles (aLDFA). Multicentre, retrospective study utilizing 81 matched radiographic and CT studies of clinical patients undergoing assessment for various issues were reviewed. Anatomic lateral distal femoral angles were measured, and accuracy assessed with descriptive statistics and Bland-Altman plot analysis, with CT considered the reference standard. Sensitivity and specificity of a cut-off for measured aLDFA (102 degrees) were determined to assess radiography as a screening tool for significant deformity. Radiographs on average overestimated aLDFA by 1.8 degrees compared to CT. Bland-Altman analysis identified a 15.4 degrees 95% limit of agreement range and a tendency for greater overestimation at higher average measured value. Radiographic measurement of aLDFA of 102 degrees or less had a 90% sensitivity, 71.83% specificity, and 98.08% negative predictive value for the CT measurement being less than 102 degrees. Accuracy of aLDFA measurement by caudocranial radiographs does not demonstrate sufficient accuracy when compared to CT frontal plane reconstructions with unpredictable differences. Radiographic assessment is a useful screening tool to exclude animals with a true aLDFA of greater than 102 degrees with a high degree of certainty.