Comparative anatomy of the proximal tibia in healthy Labrador Retrievers and Yorkshire Terriers

1) To provide specific quantitative data of tibial conformation in Labrador Retrievers and Yorkshire Terriers; 2) To compare the tibial conformation of these two breeds; and 3) To compare these data with previously reported data.

Mediolateral radiographs of the stifle were obtained from 30 consecutive Labrador Retrievers and 30 consecutive Yorkshire Terriers with an angle of extension of 135°. The tibial plateau angle (TPA), the angle between the tibial plateau and the patellar tendon (PTA), the Z angle, the distal tibial axis/proximal tibial axis angle (DPA), and the relative tibial tuberosity width (rTTW) were measured and compared among the two breeds.

The breed had a significant effect on all of the measured variables (p <0.01): Labrador Retrievers had a lower TPA (25 ± 3° compared to 30 ± 4°), a lower Z angle (58.8 ± 3.2° compared to 69.2 ± 4.5°), a lower DPA (4.5 ± 2.3° compared to 10.8 ± 4.3°), and a lower rTTW (0.74 ± 0.1 compared to 0.86 ± 0.1) than Yorkshire Terriers. The PTA was greater in Labrador Retrievers compared to Yorkshire Terriers (106.9 ± 3.9° compared to 103.7 ± 6.5°). Four correlations were found to be significant: the DPA angle was correlated with the TPA, the Z angle, and the rTTW. The TPA was also correlated with the Z angle.

The variation in tibial conformation between breeds should be taken into account when studying the role of each measured parameter in the pathology of cruciate disease. When the relevance of each of the aforementioned measured parameters is better understood, it may help determine the most appropriate surgical treatment.