Inter-Individual Variations in Radial Bowing in Beagles: Cranial and Medial Deviation Patterns

The canine radius has anatomical and clinical importance because its shape influences forelimb alignment, joint orientation, and load distribution. However, normal three-dimensional variations in radial bowing within a single breed have not been sufficiently described. This study aimed to characterise inter-individual variations in radial bowing in Beagles using three-dimensional morphometry and principal component analysis. Nineteen radial specimens from 19 Beagles were examined. Surface morphology was captured using a three-dimensional scanner, with reference points placed on the proximal and distal articular regions and at three shaft levels corresponding to 25%, 50%, and 75% of the radial length. Distances from each shaft centroid to the radial axis, sagittal plane, and dorsal plane were measured and normalised for radial length, and principal component analysis was performed using the normalised variables. The middle level of the radius showed the greatest deviation among the three shaft levels. Cranial deviation was more pronounced than mediolateral deviation, and mediolateral deviation in the dorsal plane was directed medially. Principal component analysis showed that the first two principal components explained more than 90% of the total variance. The first principal component mainly reflected cranial deviation at the middle level of the radius, whereas the second principal component reflected medial deviation at the proximal and middle levels. These findings quantitatively demonstrate inter-individual variations in radial bowing among Beagles and provide a three-dimensional anatomical basis for future studies on radial morphology, joint orientation, and orthopaedic assessment in canines.