Evaluation of Tibial Torsion in Yorkshire Terriers with and without Medial Patellar Luxation.

OBJECTIVE:
To determine if medial patellar luxation (MPL) in Yorkshire Terriers is associated with tibial torsion.
STUDY DESIGN:
Prospective cross-sectional study.
ANIMALS:
Yorkshire Terriers (n = 30; 60 tibiae).
METHODS:
Each MPL was graded using a categorical grading scheme. Computed tomography of the tibiae was performed and tibial torsion angle (TTA) was assessed. MPL grade was analyzed with a general linear model where the independent variables include sex, neutering status, age, weight, and TTA.
RESULTS:
Factors that had collective impact on MPL grade were TTA, age, and weight squared. As MPL grade increased, TTA decreased by 0.05° and age increased by 0.13 years. As weight increased, MPL decreased. There was no effect (P > .05) from scorers, side, and neutering status.
CONCLUSION:
Body weight squared, TTA, and age affect MPL grade, suggesting that a torsional deformity may contribute to the development of MPL in Yorkshire terriers along with weight and age.