The Effect of the Method of Canal Flare Index Calculation on Femoral Classification in Dogs: An Ex Vivo Study

Abstract Objectives The aim of this study was to compare canal flare index (CFI) values obtained by different intracortical widths in the lesser trochanter and to evaluate their influence on femoral classification. Methods Femur radiographic images were analysed by three evaluators that calculated the CFI using three different points in the lesser trochanter: proximal, midpoint, and distal. Results There was no interobserver influence, but there was a difference in the CFI value and femoral classification according to the calculation method. The proximal region presents higher CFI values and only 4% of ‘Stovepipe’ femurs, while the distal region presents lower CFI values and 46% of ‘Stovepipe’ femurs. Clinical Significance The variation in level of measurement can significantly alter femoral classification, which must be considered when the CFI is used in the surgical planning of total hip arthroplasty.