Ebru Eravci Yalin 1, Yusuf Altundağ 2, Kemal Altunatmaz 3, Buket Çakar 4, Esra Acar 4, Edyta Pasicka 5, Ermiş Özkan 6, Ozan Gündemir 6, Mihaela-Claudia Spataru 7
Background
The patella is crucial for limb extension and joint stability in small animals, and its morphology significantly impacts the success of orthopedic surgeries like patellar luxation repair and fracture fixation. However, comparative data on patellar shape and size in cats and dogs are scarce. Given the anatomical diversity among dog breeds, individualized surgical planning may be necessary to enhance surgical outcomes and implant fit. This study aimed to assess inter- and intraspecific differences in patellar morphology using three-dimensional geometric morphometrics to support tailored surgical approaches.
Methods
Computed tomography scans of 18 cats and 55 dogs were used to create 3D models of the right patella. Fourteen anatomical landmarks were manually placed on each model. Geometric morphometric analysis was performed using Generalized Procrustes Analysis and principal component analysis (PCA) to identify shape variation. Statistical tests, including ANOVA and multivariate regression, assessed species differences and the influence of patellar size (centroid size) on shape (allometry).
Results
Dogs exhibited significantly larger and more variable patellar sizes and shapes compared to cats. PCA revealed that the primary shape variation (PC1, 25.17%) distinguished cats and dogs, with dogs having more rectangular and thicker patellae, while cats had more triangular, slender shapes. The second principal component (16.56%) reflected intraspecific variation. Regression analysis showed a significant allometric effect, with centroid size explaining 12.2% of shape variation. Some small dogs clustered with cats in morphospace, suggesting morphological overlap in similarly sized individuals.
Limitations
Breed information was unavailable for most dogs, preventing breed-specific analysis. This limits insights into how breed diversity affects patellar morphology. Additionally, while body weight showed only a marginal association with size, functional adaptation and locomotor demands may also contribute to morphological differences.
Conclusions
Patellar morphology differs markedly between cats and dogs, with greater variability in dogs, likely due to breed diversity and functional demands. A one-size-fits-all surgical or implant approach is inadequate, especially for dogs. Geometric morphometrics offers valuable insights for personalized orthopedic planning. Future work should focus on breed-specific analyses to further optimize surgical interventions and implant designs.
Three-Dimensional modeling and landmark placement process. (1) Patellar images were obtained using computed tomography and three-dimensional models were generated. (2) Manual digitization began with the placement of two primary landmarks: one at the most superior point of the patella and the other at its central point (a). Intermediate landmarks were then placed at the anterior, posterior, medial, and lateral midpoints between these primary landmarks (b). Additional landmarks were placed halfway between each primary and intermediate point (c). (3) This resulted in a total of 14 consistently applied landmarks for each patella model
How did we do?
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