Three dimensional morphologic analysis of the lateral surface of the canine femur.

Objectives: Analyze the lateral plating surface of the femur to obtain bend and twist angles in dogs with non-chondrodystrophic phenotype.

Study Design: Retrospective computed tomography (CT) morphologic analysis.

Sample Population: Historical cohort, hindlimb CT scans (n = 30).

Materials And Methods: The CT images of 30 normal femurs were uploaded to surgical planning software and 13 points of interest and their respective bend/twist angles were identified on the lateral surfaces. Mean, standard deviation, coefficient of variation (CV), and range were calculated for each bend/twist angle. Hierarchal clustering and fast Fourier Analyses were used to segment the cohort. Distribution of age, breed, sex, and weight was evaluated between clusters with an exact Wilcoxon-Mann-Whitney test.

Results: The CV of bending ranged from 17% to 46% and for twisting ranged from 21% to 58%. The greater trochanter was the most pronounced bend on the lateral surface of the femur (mean ± SD 8.11 ± 1.35°, CV 17%), and the supracondylar region of the distal femur was the most marked twist (mean ± SD 48.98 ± 10.06°, CV 21%). Although there were no differences between dogs in proximal femur anatomy, 2 clusters of 9 and 21 dogs each were identified due to differences in bend/twist angles in the distal femur. There was no difference between clusters for age (P = .85), breed (P = .62), and sex (P = .15); however, weight differed (P = .03) but was not predictive.

Conclusion: Although distal femoral lateral surfaces varied sufficiently to result in 2 population clusters, further analysis is needed to determine if the differences prevent using the mean bending and twisting parameters as a template for clinical applications.